Nouns denoting natural objects (not man-made)
- Aare River
- a river in north central Switzerland that runs northeast into the Rhine
- Abukir Bay
- a bay on the Mediterranean Sea in northern Egypt
- abysm
- a bottomless gulf or pit; any unfathomable (or apparently unfathomable) cavity or chasm or void extending below (often used figuratively)
- abyssal zone
- the deep sea (2000 meters or more) where there is no light
- acclivity
- an upward slope or grade (as in a road)
- achondrite
- a stony meteor lacking chondrules
- acicula
- a needlelike part or structure of a plant or animal or crystal; as a spine or bristle or crystal
- Aconcagua
- the highest mountain in the western hemisphere; located in the Andes in western Argentina (22,834 feet high)
- Adam's Peak
- a mountain peak in south central Sri Lanka (7,360 feet high)
- Adirondack Mountains
- a mountain range in northeastern New York State; a popular resort area
- adjunct
- something added to another thing but not an essential part of it
- Admiralty Range
- mountains in Antarctica to the north of Victoria Land
- Adriatic Sea
- an arm of the Mediterranean between Slovenia and Croatia and Montenegro and Albania on the east and Italy on the west
- Aegean Sea
- an arm of the Mediterranean between Greece and Turkey; a main trade route for the ancient civilizations of Crete and Greece and Rome and Persia
- Aegospotamos
- a creek emptying into the Hellespont in present-day Turkey; at its mouth in 405 BC the Spartan fleet under Lysander defeated the Athenians and ended the Peloponnesian War
- aerie
- the lofty nest of a bird of prey (such as a hawk or eagle)
- aerolite
- a stony meteorite consisting of silicate minerals
- affluent
- a branch that flows into the main stream
- Africa
- the second largest continent; located to the south of Europe and bordered to the west by the South Atlantic and to the east by the Indian Ocean
- agent
- an active and efficient cause; capable of producing a certain effect
- air bubble
- a bubble of air
- airborne transmission
- a transmission mechanism in the which the infectious agent is spread as an aerosol and usually enters a person through the respiratory tract
- Aire River
- a river in northern England that flows southeast through West Yorkshire
- Alabama River
- a river in Alabama formed by the confluence of the Coosa and Tallapoosa Rivers near Montgomery; flows southwestward to become a tributary of the Mobile River
- Alaska Peninsula
- a peninsula of southwestern Alaska (a continuation of the Aleutian Islands)
- Alaska Range
- a mountain range in south central Alaska; contains Mount McKinley
- Aldebaran
- the brightest star in Taurus
- Algol
- the second brightest star in Perseus; the first known eclipsing binary
- Allegheny Mountains
- the western part of the Appalachian Mountains; extending from northern Pennsylvania to southwestern Virginia
- Allegheny River
- a river that rises in Pennsylvania and flows north into New York and then back south through Pennsylvania again to join the Monongahela River at Pittsburgh which is the beginning of the Ohio River
- alluvial deposit
- clay or silt or gravel carried by rushing streams and deposited where the stream slows down
- alluvial flat
- a flat resulting from repeated deposits of alluvial material by running water
- alp
- any high mountain
- Alpha Centauri
- brightest star in Centaurus; second nearest star to the sun
- Alpha Crucis
- the brightest star in the Southern Cross
- Alpha Geminorum
- a multiple star with 6 components; second brightest in Gemini; close to Pollux
- Alpha Orionis
- the second brightest star in Orion
- alpha particle
- a positively charged particle that is the nucleus of the helium atom; emitted from natural or radioactive isotopes
- Alpine type of glacier
- a glacier that moves down from a high valley
- Altair
- double star 15.7 light years from Earth; the brightest star in the Aquila constellation
- Altay Mountains
- a mountain range in central Asia that extends a thousand miles from Kazakhstan eastward into western Mongolia and northern China
- altocumulus
- a cumulus cloud at an intermediate altitude of 2 or 3 miles
- altostratus
- a stratus cloud at an intermediate altitude of 2 or 3 miles
- Amazon River
- a major South American river; arises in the Andes and flows eastward into the South Atlantic; the world's 2nd longest river (4000 miles)
- America
- North America and South America and Central America
- American Falls
- a part of Niagara Falls in western New York (north of Buffalo)
- ammonite
- one of the coiled chambered fossil shells of extinct mollusks
- Ancohuma
- a mountain peak in the Andes in Bolivia (20,960 feet high)
- Andaman Sea
- part of the Bay of Bengal to the west of the Malay Peninsula
- Andes
- a mountain range in South America running 5000 miles along the Pacific coast
- Andromeda
- a constellation in the northern hemisphere between Cassiopeia and Pegasus; contains the Andromeda galaxy
- Angel Falls
- the highest waterfall; has more than one leap; flow varies seasonally
- anion
- a negatively charged ion
- Annapurna
- a mountain in the Himalayas in Nepal (26,500 feet high)
- Antarctic continent
- an extremely cold continent at the south pole almost entirely below the Antarctic Circle; covered by an ice cap up to 13,000 feet deep
- Antarctic Ocean
- the southern waters surrounding Antarctica
- Antarctic Peninsula
- a large peninsula of Antarctica that extends some 1200 miles north toward South America; separates the Weddell Sea from the South Pacific
- Antares
- the brightest star in Scorpius
- anthill
- a mound of earth made by ants as they dig their nest
- antibaryon
- the antiparticle of a baryon; a hadron with a baryon number of -1
- antielectron
- an elementary particle with positive charge; interaction of a positron and an electron results in annihilation
- antilepton
- the antiparticle of a lepton
- antimeson
- the antiparticle of a meson
- antimuon
- the antiparticle of a muon; decays to positron and neutrino and antineutrino
- antineutrino
- the antiparticle of a neutrino
- antineutron
- the antiparticle of a neutron
- antiparticle
- a particle that has the same mass as another particle but has opposite values for its other properties; interaction of a particle and its antiparticle results in annihilation and the production of radiant energy
- antiproton
- an unstable negatively charged proton; the antiparticle of a proton
- antiquark
- the antiparticle of a quark
- antitauon
- an antilepton of very great mass
- Antlia
- a faint constellation in the southern hemisphere near Hydra and Vela
- Apalachicola River
- a river in northwestern Florida formed by the confluence of the Chattahoochee River and the Flint River at the Florida border
- Apennines
- a mountain range extending the length of the Italian peninsula
- aperture
- a natural opening in something
- Apollo asteroid
- an asteroid whose orbit crosses the Earth's orbit
- Appalachian Mountains
- a mountain range in the eastern United States extending from Quebec to the Gulf of Mexico; a historic barrier to early westward expansion of the United States
- Apus
- a constellation in the polar region of the southern hemisphere near Octans
- Aquarius
- a zodiacal constellation in the southern hemisphere; between Capricornus and Pisces
- aquifer
- underground bed or layer yielding ground water for wells and springs etc
- Aquila
- a constellation in the Milky Way near Cygnus; contains the star Altair
- Ara
- a constellation in the southern hemisphere near Telescopium and Norma
- Arabian Sea
- a northwestern arm of the Indian Ocean between India and Arabia
- Arafura Sea
- a part of the western Pacific Ocean to the north of Australia and to the south of New Guinea and the eastern islands of Indonesia
- Araguaia River
- a river in central Brazil that flows generally northward (with many falls) to join the Tocantins River
- Arauca
- a river that rises in northern Colombia and flows generally eastward to the Orinoco in central Venezuela
- Araxes
- a river that rises in northeastern Turkey (near the source of the Euphrates) and flows generally eastward through Armenia to the Caspian Sea; ancient name was Araxes
- archeological remains
- a relic that has been excavated from the soil
- archipelago
- a group of many islands in a large body of water
- Arctic Ocean
- ice covered waters surrounding the North Pole; mostly covered with solid ice or with ice floes and icebergs
- Arcturus
- the 4th brightest star and the brightest star in the constellation Bootes; 36 light-years from Earth
- arete
- a sharp narrow ridge found in rugged mountains
- Argo
- formerly a large constellation in the southern hemisphere between Canis Major and the Southern Cross; now divided into Carina and Pyxis and Puppis and Vela
- Argun River
- a river in eastern Asia that arises in China and flows northeast along the border between China and Russia to become a tributary of the Amur River
- Aries
- a small zodiacal constellation in the northern hemisphere; between Pisces and Taurus
- Aristarchus
- a bright crater on the Moon
- Arkansas River
- a river that rises in the Rocky Mountains in Colorado and flows southeast through Kansas and Oklahoma and through Arkansas to become a tributary of the Mississippi River
- Arno River
- a river in central Italy rising in the Apennines and flowing through Florence and Pisa to the Ligurian Sea
- arroyo
- a stream or brook
- Asia
- the largest continent with 60% of the earth's population; it is joined to Europe on the west to form Eurasia; it is the site of some of the world's earliest civilizations
- asterism
- (astronomy) a cluster of stars (or a small constellation)
- asteroid
- any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter)
- Asterope
- one of the stars in the star cluster Pleiades
- asthenosphere
- the lower layer of the crust
- Atacama Trench
- a depression in the floor of the Pacific Ocean off the coast of Chile
- Atlantic Coast
- a coast of the Atlantic Ocean
- Atlantic Ocean
- the 2nd largest ocean; separates North and South America on the west from Europe and Africa on the east
- Atlas Mountains
- a mountain range in northern Africa between the Mediterranean and the Sahara Desert; extends from southwestern Morocco to northern Tunisia
- atmosphere
- the envelope of gases surrounding any celestial body
- atoll
- an island consisting of a circular coral reef surrounding a lagoon
- Australia
- the smallest continent; between the South Pacific and the Indian Ocean
- Australian Alps
- a range of mountains in Australia that forms the southern end of the Great Dividing Range
- b-meson
- exceedingly short-lived meson
- backwater
- a body of water that was created by a flood or tide or by being held or forced back by a dam
- badlands
- deeply eroded barren land
- Baffin Bay
- a body of water between Greenland and northeastern Canada; connected with the Arctic Ocean to the north and with the Atlantic Ocean (via the Labrador Sea) to the south; icebound in winter
- Balkan Mountain Range
- the major mountain range of Bulgaria and the Balkan Peninsula
- Baltic Sea
- a sea in northern Europe; stronghold of the Russian navy
- bank
- a long ridge or pile
- bank
- sloping land (especially the slope beside a body of water)
- bank
- a slope in the turn of a road or track; the outside is higher than the inside in order to reduce the effects of centrifugal force
- bar
- a submerged (or partly submerged) ridge in a river or along a shore
- barbecue pit
- a pit where wood or charcoal is burned to make a bed of hot coals suitable for barbecuing meat
- Barents Sea
- the part of the Arctic Ocean to the north of Norway and Russia
- barrier
- anything serving to maintain separation by obstructing vision or access
- barrier island
- a long narrow sandy island (wider than a reef) running parallel to the shore
- barrier reef
- a long coral reef near and parallel to the shore
- baryon
- any of the elementary particles having a mass equal to or greater than that of a proton and that participate in strong interactions; a hadron with a baryon number of +1
- base
- the bottom or lowest part
- basin
- a natural depression in the surface of the land often with a lake at the bottom of it
- bathyal district
- the steep descent of the seabed from the continental shelf to the abyssal zone
- Bay of Bengal
- an arm of the Indian Ocean to the east of India
- Bay of Biscay
- an arm of the Atlantic Ocean in western Europe; bordered by the west coast of France and the north coast of Spain
- Bay of Fundy
- a bay of the North Atlantic between New Brunswick and Nova Scotia; noted for rapid tides as great as 70 feet
- Bay of Naples
- an arm of the Tyrrhenian Sea at Naples
- bay
- an indentation of a shoreline larger than a cove but smaller than a gulf
- bayou
- a swampy arm or slow-moving outlet of a lake (term used mainly in Mississippi and Louisiana)
- beach
- an area of sand sloping down to the water of a sea or lake
- beachfront
- a strip of land running along a beach
- Beaufort Sea
- part of the Arctic Ocean to the northeast of Alaska
- beauty quark
- a quark with a charge of -1/3 and a mass about 10,000 times that of an electron
- bed
- (geology) a stratum of rock (especially sedimentary rock)
- bed
- a depression forming the ground under a body of water
- bedrock
- solid unweathered rock lying beneath surface deposits of soil
- beehive
- a structure that provides a natural habitation for bees; as in a hollow tree
- belay
- something to which a mountain climber's rope can be secured
- belt
- a path or strip (as cut by one course of mowing)
- ben
- a mountain or tall hill
- bench
- a level shelf of land interrupting a declivity (with steep slopes above and below)
- berg
- a large mass of ice floating at sea; usually broken off of a polar glacier
- Bering Sea
- part of the North Pacific between Alaska and Siberia; connected to the Arctic Ocean by the Bering Strait
- Bering Strait
- a strait connecting the Bering Sea to the Arctic Ocean
- Berkshire Hills
- a low mountain range in western Massachusetts; a resort area
- berm
- a narrow ledge or shelf typically at the top or bottom of a slope
- Beta Centauri
- the second brightest star in Centaurus
- Beta Crucis
- the second brightest star in the Southern Cross
- Beta Orionis
- the brightest star in Orion
- beta particle
- a high-speed electron or positron emitted in the decay of a radioactive isotope
- Big Sioux River
- a river that rises in northeastern South Dakota and flows southward to join the Missouri River at Sioux City, Iowa
- Bighorn River
- a river that flows from central Wyoming to the Yellowstone River in southern Montana
- bight
- a broad bay formed by an indentation in the shoreline
- Bight of Benin
- a broad indentation of the Gulf of Guinea in western Africa
- bilestone
- a calculus formed in the gall bladder or its ducts
- billabong
- a branch of a river made by water flowing from the main stream only when the water level is high
- billabong
- a stagnant pool of water in the bed of a stream that flows intermittently
- binary
- a system of two stars that revolve around each other under their mutual gravitation
- biohazard
- any bacterium or virus or toxin that could be used in biological warfare
- bird nest
- nest where birds lay their eggs and hatch their young
- Biscayne Bay
- a narrow bay formed by an inlet from the Atlantic Ocean in southeastern Florida
- Bismarck Sea
- an arm of the South Pacific to the southwest of the Bismarck Archipelago
- bit
- a small fragment of something broken off from the whole
- black body
- a hypothetical object capable of absorbing all the electromagnetic radiation falling on it
- Black Forest
- a hilly forest region in southwestern Germany
- Black Hills
- mountains in southwestern South Dakota and northeastern Wyoming; sacred to the Sioux (whites settling in the Black Hills led to the Battle of Little Bighorn); site of Mount Rushmore
- black hole
- a region of space resulting from the collapse of a star; extremely high gravitational field
- bladder stone
- a calculus formed in the bladder
- blade
- something long and thin resembling a blade of grass
- blanket
- anything that covers
- blood-brain barrier
- a mechanism that creates a barrier between brain tissues and circulating blood; serves to protect the central nervous system
- Blue Nile
- a headstream of the Nile; joins the White Nile at Khartoum to form the Nile
- Blue Ridge Mountains
- a range of the Appalachians extending from southern Pennsylvania to northern Georgia
- blue
- the sky as viewed during daylight
- bluff
- a high steep bank (usually formed by river erosion)
- body
- an individual 3-dimensional object that has mass and that is distinguishable from other objects
- body of water
- the part of the earth's surface covered with water (such as a river or lake or ocean)
- bog
- wet spongy ground of decomposing vegetation; has poorer drainage than a swamp; soil is unfit for cultivation but can be cut and dried and used for fuel
- bolt-hole
- a hole through which an animal may bolt when pursued into its burrow or den
- bonanza
- an especially rich vein of precious ore
- Bonete
- a mountain in the Andes in Argentina (22,546 feet high)
- Bootes
- a constellation in the northern hemisphere near Ursa Major
- borrow pit
- a pit created to provide earth that can be used as fill at another site
- boson
- any particle that obeys Bose-Einstein statistics but not the Pauli exclusion principle; all nuclei with an even mass number are bosons
- Bosporus
- a strait connecting the Mediterranean and the Black Sea; separates the European and Asian parts of Turkey; an important shipping route
- bottom
- low-lying alluvial land near a river
- Bougainville Trench
- a depression in the floor of the Pacific Ocean between New Guinea and the Solomon Islands
- boulder
- a large smooth mass of rock detached from its place of origin
- brae
- a slope or hillside
- Brahmaputra River
- an Asian river; flows into the Bay of Bengal
- branch
- a stream or river connected to a larger one
- branched chain
- an open chain of atoms with one or more side chains attached to it
- Brazos River
- a river that rises in Mexico and flows across Texas into the Gulf of Mexico
- breach
- an opening (especially a gap in a dike or fortification)
- break
- (geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other
- Brenner Pass
- an Alpine mountain pass connecting Innsbruck in Austria with Bolzano in Italy that has long been a route for trade and for invasions
- brickbat
- a fragment of brick used as a weapon
- briny
- any very large body of (salt) water
- Bristol Channel
- an inlet of the Atlantic Ocean between southern Wales and southwestern England
- brook
- a natural stream of water smaller than a river (and often a tributary of a river)
- brooklet
- a small brook
- bubble
- a hollow globule of gas (e.g., air or carbon dioxide)
- buffalo chip
- a piece of dried bovine dung
- building block
- a single undivided natural thing occurring in the composition of something else
- bullet hole
- a hole made by a bullet passing through it
- burrow
- a hole made by an animal, usually for shelter
- butte
- a hill that rises abruptly from the surrounding region; has a flat top and sloping sides
- Buzzards Bay
- an inlet of the Atlantic Ocean in southeastern Massachusetts
- Cachi
- a mountain in the Andes in Argentina (22,047 feet high)
- Caelum
- a constellation in the southern hemisphere near Columba and Eridanus
- calculus
- a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body
- calculus
- an incrustation that forms on the teeth and gums
- caldera
- a large crater caused by the violent explosion of a volcano that collapses into a depression
- Callisto
- the second largest of Jupiter's satellites
- Caloosahatchee River
- a river in southern Florida that flows westerly to the Gulf of Mexico; forms the western end of the Cross-Florida Waterway
- Cam River
- a river in east central England that flows past Cambridge to join the Ouse River
- Cambrian Mountains
- a rugged plateau that runs north to south through central Wales
- Canadian River
- a river rising in northeastern New Mexico and flowing eastward across the Texas panhandle to become a tributary of the Arkansas River in Oklahoma
- canal
- (astronomy) an indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion
- Cancer
- a small zodiacal constellation in the northern hemisphere; between Leo and Gemini
- Canis Major
- a constellation to the southeast of Orion; contains Sirius
- Canis Minor
- a constellation to the east of Orion; contains Procyon
- canon
- a ravine formed by a river in an area with little rainfall
- Canopus
- supergiant star 650 light years from Earth; second brightest star in the sky
- Cantabrian Mountains
- a range of mountains in northern Spain along the coast of the Bay of Biscay
- Canton River
- a river in southeast China that flows into the South China Sea
- canyonside
- the steeply sloping side of a canyon
- cap
- a protective covering that is part of a plant
- Cape Canaveral
- a sandy promontory (formerly Cape Kennedy) extending into the Atlantic Ocean from a barrier island off the eastern coast of Florida; the site of a NASA center for spaceflight
- Cape Cod Bay
- the southern part of Massachusetts Bay
- Cape Fear River
- a river in North Carolina that flows southeast to the Atlantic Ocean at Cape Fear
- Cape Sable
- a promontory on the far southern part of Nova Scotia
- Cape Sable
- a cape at the southwest tip of Florida; the southernmost part of the United States mainland
- Cape Trafalgar
- a small cape in southwestern Spain
- Cape York
- the northern tip of Cape York Peninsula at the Torres Strait; the northernmost point of the Australian mainland
- Cape York Peninsula
- a peninsula in Queensland in northeastern Australia between the Gulf of Carpentaria and the Coral Sea
- cape
- a strip of land projecting into a body of water
- Capella
- the brightest star in Auriga
- Capricornus
- a faint zodiacal constellation in the southern hemisphere; between Sagittarius and Aquarius
- Caribbean Sea
- an arm of the Atlantic Ocean between North and South America; the origin of the Gulf stream
- Carina
- a keel-shaped constellation in the southern hemisphere; contains the star Canopus
- Carlsbad Caverns
- a group of caverns in southeastern New Mexico noted for their stalactites and stalagmites
- Carpathian Mountains
- a mountain range in central Europe that extends from Slovakia and southern Poland southeastward through western Ukraine to northeastern Romania; a popular resort area
- carpet
- a natural object that resembles or suggests a carpet
- cascade
- a small waterfall or series of small waterfalls
- Cascade Mountains
- a mountain range in the northwestern United States extending through Washington and Oregon and northern California; a part of the Coast Range
- Caspian Sea
- a large saltwater lake between Iran and Russia fed by the Volga River; the largest inland body of water in the world
- Cassiopeia
- a W-shaped constellation in the northern hemisphere near Polaris
- cataract
- a large waterfall; violent rush of water over a precipice
- Cataract Canyon
- a tributary of the Grand Canyon
- catch
- anything that is caught (especially if it is worth catching)
- cation
- a positively charged ion
- Catskill Mountains
- a range of the Appalachians to the west of the Hudson in southeastern New York; includes many popular resort areas
- Caucasus Mountains
- the mountain range in Caucasia between the Black Sea and the Caspian Sea that forms part of the traditional border between Europe and Asia
- cave
- a geological formation consisting of an underground enclosure with access from the surface of the ground or from the sea
- cavern
- a large cave or a large chamber in a cave
- cavern
- any large dark enclosed space
- cavity
- a sizeable hole (usually in the ground)
- celestial body
- natural objects visible in the sky
- cellular inclusion
- any small intracellular body found within another (characteristic of certain diseases)
- Centaurus
- a conspicuous constellation in the southern hemisphere near the Southern Cross
- Cepheus
- a faint constellation in the northern hemisphere near Cassiopeia and the pole star
- Ceres
- the largest asteroid and the first discovered
- Cetus
- a large constellation on the equator near Pisces and Aquarius
- chain
- a series of hills or mountains
- chain
- (chemistry) a series of linked atoms (generally in an organic molecule)
- Chamaeleon
- a faint constellation in the polar region of the southern hemisphere near Apus and Mensa
- champaign
- extensive tract of level open land
- Changtzu
- a mountain in the central Himalayas on the border of Tibet and Nepal (24,780 feet high)
- channel
- a deep and relatively narrow body of water (as in a river or a harbor or a strait linking two larger bodies) that allows the best passage for vessels
- Chao Phraya
- a river in Thailand formed by the confluence of the Nan and Ping Rivers; flows southward past Bangkok and empties into the Gulf of Thailand
- chap
- a crack in a lip caused usually by cold
- Chari River
- an African river that flows northwest into Lake Chad
- Charioteer
- a conspicuous constellation in the northern hemisphere; between Great Bear and Orion at edge of Milky Way
- Charles River
- a river in eastern Massachusetts that empties into Boston Harbor and that separates Cambridge from Boston
- Charles's Wain
- a group of seven bright stars in the constellation Ursa Major
- charm quark
- a quark with an electric charge of +2/3 and a mass 2900 times that of an electron and a charm of +1
- chasm
- a deep opening in the earth's surface
- Chattahoochee River
- a river rising in northern Georgia and flowing southwest and south to join the Flint River at the Florida border where they form the Apalachicola River
- Chesapeake Bay
- a large inlet of the North Atlantic between Virginia and Maryland; fed by Susquehanna River
- Chimborazo
- a mountain peak in the Andes in Ecuador (20,560 feet high)
- chink
- a narrow opening as e.g. between planks in a wall
- Chiron
- an asteroid discovered in 1977; it is unique in having an orbit lying mainly between the orbits of Saturn and Uranus
- chondrite
- a rock of meteoric origin containing chondrules
- chondrule
- small granule (of e.g. chrysolite) found in some meteoric rocks
- chromosphere
- a gaseous layer of the sun's atmosphere (extending from the photosphere to the corona) that is visible during a total eclipse of the sun
- chuckhole
- a pit or hole produced by wear or weathering (especially in a road surface)
- Chukchi Peninsula
- peninsula of northeastern Siberia across the Bering Strait from northwestern Alaska
- Chukchi Sea
- part of the Arctic Ocean just to the north of the Bering Strait
- Cimarron River
- a river that rises in northeastern New Mexico and flows eastward into Oklahoma where it becomes a tributary of the Arkansas River
- cinder
- a fragment of incombustible matter left after a wood or coal or charcoal fire
- Circinus
- a small faint constellation in the southern hemisphere near Musca and Triangulum Australe
- cirque
- a steep-walled semicircular basin in a mountain; may contain a lake
- cirrocumulus
- a cloud at a high altitude consisting of a series of regularly arranged small clouds resembling ripples
- cirrostratus
- a thin uniform layer of hazy cloud at high altitude
- cirrus
- a wispy white cloud (usually of fine ice crystals) at a high altitude (4 to 8 miles)
- clast
- (geology) a constituent fragment of a clastic rock
- clastic rock
- (geology) a rock composed of broken pieces of older rocks
- cleft
- a long narrow opening
- cliff
- a steep high face of rock
- Clinch River
- a river that rises in southwestern Virginia and flows generally southwestward across eastern Tennessee to the Tennessee River
- closed chain
- (chemistry) a chain of atoms in a molecule that forms a closed loop
- closed universe
- (cosmology) a universe that is spatially closed and in which there is sufficient matter to halt the expansion that began with the big bang; the visible matter is only 10 percent of the matter required for closure but there may be large amounts of dark matter
- cloud
- a visible mass of water or ice particles suspended at a considerable altitude
- cloud bank
- a layer of clouds seen from a distance
- Clyde
- a river in western Scotland that flows from the southern uplands into the Firth of Clyde; navigable by oceangoing vessels as far as Glasgow
- coal
- a hot fragment of wood or coal that is left from a fire and is glowing or smoldering
- coast
- a slope down which sleds may coast
- Coast Mountains
- a string of mountain ranges along the Pacific coast of North America from southeastern Alaska to Lower California
- coast
- the shore of a sea or ocean
- coastal plain
- a plain adjacent to a coast
- coastland
- land in a coastal area
- Coeur d'Alene Lake
- a lake in northern Idaho
- coffee grounds
- the dregs remaining after brewing coffee
- col
- a pass between mountain peaks
- collector
- a crater that has collected cosmic material hitting the earth
- collision course
- a course of a moving object that will lead to a collision if it continues unchanged
- Colorado Plateau
- a large plateau to the south and west of the Rocky Mountains; abuts mountains on the north and east and ends in an escarpment overlooking lowlands to the south and west; the Grand Canyon is carved out of the southwestern corner
- Colorado River
- an important river in the southwestern United States; rises in the Rocky Mountains of northern Colorado and flows southwest through Utah into Arizona (where it flows through the Grand Canyon) and then southward through the southern tip of Nevada, then forming the border between California and Arizona and finally into Mexico where it empties into the Gulf of California; the main source of water in the southwestern United States
- Colorado River
- a river in Texas; flows southeast into the Gulf of Mexico
- Columba
- a constellation in the southern hemisphere near Puppis and Caelum
- Columbia River
- a North American river; rises in southwestern Canada and flows southward across Washington to form the border between Washington and Oregon before emptying into the Pacific; known for its salmon runs in the spring
- coma
- (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed
- Coma Berenices
- a constellation in the northern hemisphere between Ursa Major and Bootes; contains a cluster of some 10,000 galaxies
- comet
- (astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
- commemorative
- an object (such as a coin or postage stamp) made to mark an event or honor a person
- common fault
- an inclined fault in which the hanging wall appears to have slipped downward relative to the footwall
- condensation trail
- an artificial cloud created by an aircraft; caused either by condensation due to the reduction in air pressure above the wing surface or by water vapor in the engine exhaust
- Congo River
- a major African river (one of the world's longest); flows through Congo into the South Atlantic
- Connecticut River
- a river in the northeastern United States; flows south from northern New Hampshire along the border between New Hampshire and Vermont and through Massachusetts and Connecticut where it empties into Long Island Sound
- consolidation
- something that has consolidated into a compact mass
- constellation
- a configuration of stars as seen from the earth
- continent
- one of the large landmasses of the earth
- continental glacier
- a glacier that spreads out from a central mass of ice
- continental shelf
- the relatively shallow (up to 200 meters) seabed surrounding a continent
- Cook Strait
- a narrow strait separating the North Island and South Island in New Zealand
- Coosa River
- river that rises in northwestern Georgia and flows southwest through eastern Alabama to join the Tallapoosa River near Montgomery and form the Alabama River
- Copernicus
- a conspicuous crater on the Moon
- coprolite
- fossil excrement; petrified dung
- coprolith
- a hard mass of fecal matter
- coral reef
- a reef consisting of coral consolidated into limestone
- Coral Sea
- an arm of the South Pacific to the northeast of Australia
- core
- the central part of the Earth
- core
- a cylindrical sample of soil or rock obtained with a hollow drill
- corner
- a projecting part where two sides or edges meet
- Corona Borealis
- a small constellation in the northern hemisphere between Bootes and Hercules
- Coropuna
- a mountain peak in the Andes in Peru (21,083 feet high)
- Corvus
- a small quadrilateral constellation in the southern hemisphere near Virgo
- cosmic string
- (cosmology) a hypothetical one-dimensional subatomic particle having a concentration of energy and the dynamic properties of a flexible loop
- cosmos
- everything that exists anywhere
- couple
- (physics) something joined by two equal and opposite forces that act along parallel lines
- course
- a line or route along which something travels or moves
- cove
- a small inlet
- cove
- small or narrow cave in the side of a cliff or mountain
- cover
- a natural object that covers or envelops
- Crab Nebula
- a remnant of a supernova detected first in 1054 AD
- crag
- a steep rugged rock or cliff
- Crane
- a small constellation in the southern hemisphere near Phoenix
- cranny
- a small opening or crevice (especially in a rock face or wall)
- crater
- a bowl-shaped depression formed by the impact of a meteorite or bomb
- Crater
- a faint constellation in the southern hemisphere near Hydra and Corvus
- crater
- a bowl-shaped geological formation at the top of a volcano
- craton
- the part of a continent that is stable and forms the central mass of the continent; typically Precambrian
- creek bed
- a channel occupied (or formerly occupied) by a stream
- crevasse
- a deep fissure
- Crocodile River
- an African river; flows into the Indian Ocean
- Cross-Florida Waterway
- a waterway used by small boats to travel between the Atlantic Ocean and the Gulf of Mexico through Lake Okeechobee and the Caloosahatchee Canal and the Caloosahatchee River
- crossing
- a shallow area in a stream that can be forded
- crust
- a hard outer layer that covers something
- crustal plate
- a rigid layer of the Earth's crust that is believed to drift slowly
- Crux Australis
- a small conspicuous constellation in the southern hemisphere in the Milky Way near Centaurus
- crystal
- a rock formed by the solidification of a substance; has regularly repeating internal structure; external plane faces
- crystallite
- any of numerous minute rudimentary crystalline bodies of unknown composition found in glassy igneous rock
- cultivated land
- arable land that is worked by plowing and sowing and raising crops
- Cumberland Gap
- a pass through the Cumberland Mountains between Virginia and Kentucky that early settlers used in order to move west
- Cumberland Mountains
- the southwestern part of the Appalachians
- Cumberland River
- a river that rises in southeastern Kentucky and flows westward through northern Tennessee to become a tributary of the Ohio River in southwestern Kentucky
- cumulonimbus
- a dark cloud of great vertical extent charged with electricity; associated with thunderstorms
- cumulus
- a globular cloud
- Cuquenan Falls
- a famous waterfall in Venezuela
- curtain
- any barrier to communication or vision
- cutting
- a piece cut off from the main part of something
- Cygnus
- a constellation in the northern hemisphere between Pegasus and Draco in the Milky Way; contains a black hole
- dale
- an open river valley (in a hilly area)
- dander
- small scales from animal skins or hair or bird feathers that can cause allergic reactions in some people
- dandruff
- loose scales shed from the scalp
- Danube River
- the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea
- Darling River
- an Australian river; tributary of the Murray River
- Daryacheh-ye Orumiyeh
- a shallow saline lake in northwestern Iran between Tabriz and the western border of Turkey
- Davy Jones's locker
- the bottom of a sea or ocean
- Dead Sea
- a saltwater lake on the border between Israel and Jordan; its surface in 1292 feet below sea level
- declension
- a downward slope or bend
- deep
- literary term for an ocean
- deep
- a long steep-sided depression in the ocean floor
- defile
- a narrow pass (especially one between mountains)
- Deimos
- the outer of two small satellites of Mars
- Delaware Bay
- an inlet of the North Atlantic; fed by the Delaware River
- Delaware River
- a river that rises in the Catskills in southeastern New York and flows southward along the border of Pennsylvania with New York and New Jersey to northern Delaware where it empties into Delaware Bay
- dell
- a small wooded hollow
- Delphinus
- a constellation in the northern hemisphere near Pegasus and Aquila
- delta
- a low triangular area of alluvial deposits where a river divides before entering a larger body of water
- delta ray
- an electron ejected from matter by ionizing radiation
- Demerara
- a river in northern Guyana that flows northward into the Atlantic
- Denali Fault
- a major open geological fault in Alaska
- Deneb
- the brightest star in Cygnus
- Denebola
- a star in Leo approximately 43 light years from Earth
- deposit
- matter that has been deposited by some natural process
- depression
- a sunken or depressed geological formation
- desideratum
- something desired as a necessity
- Detroit River
- a short river flowing from Lake St. Clair to Lake Erie along the border between the United States and Canada; one the busiest inland waterways in the world
- deuteron
- the nucleus of deuterium; consists of one proton and one neutron; used as a bombarding particle in accelerators
- Dhaulagiri
- a mountain in the Himalayas in Nepal (26,820 feet high)
- diapir
- a domed rock formation where a core of rock has moved upward and pierced through the more brittle overlying strata
- diffuse nebula
- a cluster of stars within an intricate cloud of gas and dust
- dipole
- a pair of equal and opposite electric charges or magnetic poles separated by a small distance
- dipole molecule
- a molecule that is a permanent dipole
- direct transmission
- a transmission mechanism in which the infectious agent is transferred directly into the body via touching or biting or kissing or sexual intercourse or by droplets entering the eye or nose or mouth
- discard
- anything that is cast aside or discarded
- distributary
- a branch of a river that flows away from the main stream and does not rejoin it
- ditch
- any small natural waterway
- divot
- a piece of turf dug out of a lawn or fairway (by an animals hooves or a golf club)
- divot
- (golf) the cavity left when a piece of turf is cut from the ground by the club head in making a stroke
- Dnieper River
- a river that rises in Russia near Smolensk and flowing south through Belarus and Ukraine to empty into the Black Sea
- dog do
- fecal droppings from a dog
- Dog Star
- the brightest star in the sky; in Canis Major
- Dolomite Alps
- an eastern range of the Alps in northeastern Italy famous for their dolomitic limestone
- Don River
- a European river in southwestern Russia; flows into the Sea of Azov
- Donner Pass
- a mountain pass in northeastern California near Lake Tahoe; site where in 1844 some members of an emigrant party survived by eating those who had died
- Dorado
- a constellation in the southern hemisphere near Reticulum and Pictor; contains most of the Large Magellanic Cloud
- down
- (usually plural) a rolling treeless highland with little soil
- down quark
- a stable quark with an electric charge of -1/3 and a mass 607 times that of an electron
- downhill
- the downward slope of a hill
- Dragon
- a faint constellation twisting around the north celestial pole and lying between Ursa Major and Cepheus
- draw
- a gully that is shallower than a ravine
- dregs
- sediment that has settled at the bottom of a liquid
- drey
- the nest of a squirrel
- drift
- a large mass of material that is heaped up by the wind or by water currents
- drift ice
- masses of ice floating in the open sea
- drink
- any large deep body of water
- drumlin
- a mound of glacial drift
- dry land
- the solid part of the earth's surface
- dry wash
- the dry bed of an intermittent stream (as at the bottom of a canyon)
- dune
- a ridge of sand created by the wind; found in deserts or near lakes and oceans
- Earth's crust
- the outer layer of the Earth
- Earth's surface
- the outermost level of the land or sea
- earth
- the 3rd planet from the sun; the planet we live on
- East China Sea
- part of the Pacific Ocean near eastern Asia
- Ebro River
- a river in northeastern Spain; flows into the Mediterranean
- Edgeworth-Kuiper belt
- a disk-shaped region of minor planets outside the orbit of Neptune
- eggshell
- the exterior covering of a bird's egg
- El Libertador
- a mountain in the Andes in Argentina (22,047 feet high)
- El Muerto
- a mountain peak in the Andes on the border between Argentina and Chile (21,457 feet high)
- Elbe River
- a river in central Europe that arises in northwestern Czechoslovakia and flows northward through Germany to empty into the North Sea
- electric dipole
- a dipole with equal and opposite electric charges
- electron
- an elementary particle with negative charge
- elementary particle
- (physics) a particle that is less complex than an atom; regarded as constituents of all matter
- elevation
- a raised or elevated geological formation
- eliminator
- an agent that eliminates something
- Elizabeth River
- a short river in southeastern Virginia flowing between Norfolk and Portsmouth into Hampton Roads
- enclosure
- a naturally enclosed space
- English Channel
- an arm of the Atlantic Ocean that forms a channel between France and Britain
- enlivener
- an agent that gives or restores life or vigor
- enterolith
- a calculus occurring in the intestines
- envelope
- a natural covering (as by a fluid)
- Epsilon Aurigae
- the largest known star
- Eridanus
- a constellation in the southern hemisphere near Fornax and Cetus
- escarpment
- a long steep slope or cliff at the edge of a plateau or ridge; usually formed by erosion
- esker
- (geology) a long winding ridge of post glacial gravel and other sediment; deposited by meltwater from glaciers or ice sheets
- essential
- anything indispensable
- estraterrestrial body
- a natural object existing outside the earth and outside the earth's atmosphere
- estuary
- the wide part of a river where it nears the sea; fresh and salt water mix
- Euphrates River
- a river in southwestern Asia; flows into the Persian Gulf; was important in the development of several great civilizations in ancient Mesopotamia
- Eurasia
- the land mass formed by the continents of Europe and Asia
- Europa
- the 4th largest of Jupiter's satellites; covered with a smooth shell of frozen water
- Europe
- the 2nd smallest continent (actually a vast peninsula of Eurasia); the British use `Europe' to refer to all of the continent except the British Isles
- Euxine Sea
- a sea between Europe and Asia; a popular resort area of eastern Europeans
- Everglades
- a large subtropical swamp in southern Florida that is noted for its wildlife
- exfoliation
- a thin flake of dead epidermis shed from the surface of the skin
- exosphere
- the outermost atmospheric layer
- expanse
- a wide and open space or area as of surface or land or sky
- Eyre Peninsula
- a peninsula of southern Australia
- fallow
- cultivated land that is not seeded for one or more growing seasons
- falls
- a steep descent of the water of a river
- fatigue crack
- a crack in metal resulting from metal fatigue
- fen
- low-lying wet land with grassy vegetation; usually is a transition zone between land and water
- fermion
- any particle that obeys Fermi-Dirac statistics and is subject to the Pauli exclusion principle
- filing
- a fragment rubbed off by the use of a file
- finding
- something that is found
- Fingal's Cave
- a large cave with basaltic pillars on Staffa island in Scotland
- fiord
- a long narrow inlet of the sea between steep cliffs; common in Norway
- fire pit
- a pit whose floor is incandescent lava
- fireball
- the luminous center of a nuclear explosion
- fireball
- a ball of fire (such as the sun or a ball-shaped discharge of lightning)
- firestone
- a sandstone that withstands intense heat; used to line fireplaces and furnaces and kilns
- firth
- a long narrow estuary (especially in Scotland)
- Firth of Clyde
- a firth on the southwestern coast of Scotland emptying into the North Channel
- Firth of Forth
- a large firth on the east coast of Scotland and the estuary of the Forth River; location of Edinburgh
- fishpond
- a freshwater pond with fish
- fixed star
- any star in the Ptolemaic theory of planetary motion
- flare star
- a red dwarf star in which luminosity can change several magnitudes in a few minutes
- flat
- a level tract of land
- Flint River
- a river in western Georgia that flows generally south to join the Chattahoochee River at the Florida border where they form the Apalachicola River
- floater
- an object that floats or is capable of floating
- floe
- a flat mass of ice (smaller than an ice field) floating at sea
- flood plain
- a low plain adjacent to a river that is formed chiefly of river sediment and is subject to flooding
- floor
- the bottom surface of any lake or other body of water
- floor
- the ground on which people and animals move about
- floor
- the lower inside surface of any hollow structure
- Florida key
- a coral reef off the southern coast of Florida
- flowage
- a body of water that has been created by deliberately flooding an area
- flume
- a narrow gorge with a stream running through it
- foam
- a mass of small bubbles formed in or on a liquid
- folium
- a thin layer or stratum of (especially metamorphic) rock
- fomite
- any inanimate object (as a towel or money or clothing or dishes or books or toys etc.) that can transmit infectious agents from one person to another
- foothill
- a relatively low hill on the lower slope of a mountain
- footwall
- the lower wall of an inclined fault
- foreland
- land forming the forward margin of something
- foreland
- a natural elevation (especially a rocky one that juts out into the sea)
- foreshore
- the part of the seashore between the highwater mark and the low-water mark
- forest
- land that is covered with trees and shrubs
- formation
- (geology) the geological features of the earth
- Fornax
- a faint constellation in the southern hemisphere near Cetus and Phoenix
- Forth River
- a river in southern Scotland that flows eastward to the Firth of Forth
- fossil
- the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil
- Fountain of Youth
- a fountain described in folk tales as able to make people young again
- fountain
- a natural flow of ground water
- Fox River
- a river in Wisconsin that flows into Lake Michigan
- fragment
- a piece broken off or cut off of something else
- free electron
- electron that is not attached to an atom or ion or molecule but is free to move under the influence of an electric field
- Galan
- a mountain peak in the Andes in Argentina (21,654 feet high)
- Galilean satellite
- one of the four satellites of Jupiter that were discovered by Galileo
- Galveston Bay
- an arm of the Gulf of Mexico in Texas to the south of Houston
- Galway Bay
- a bay of the North Atlantic on the west coast of Ireland
- Ganges River
- an Asian river; rises in the Himalayas and flows east into the Bay of Bengal; a sacred river of the Hindus
- Ganymede
- the largest of Jupiter's satellites
- gap
- an open or empty space in or between things
- Garonne River
- a river that rises in the Pyrenees and flows northwest to the Bay of Biscay
- Gasherbrum
- a mountain in northern Kashmir (26,470 feet high)
- gauge boson
- a particle that mediates the interaction of two elementary particles
- Gemini
- a zodiacal constellation in the northern hemisphere between Taurus and Cancer on the ecliptic
- gene delivery vector
- a vector for delivering genes into cells
- geode
- (mineralogy) a hollow rock or nodule with the cavity usually lined with crystals
- geosphere
- the solid part of the earth consisting of the crust and outer mantle
- geyser
- a spring that discharges hot water and steam
- giant
- a very bright star of large diameter and low density (relative to the Sun)
- Gila River
- a river that rises in western New Mexico and flows westward through southern Arizona to become a tributary of the Colorado River
- glacial boulder
- a boulder that has been carried by a glacier to a place far distant from its place of origin
- glacier
- a slowly moving mass of ice
- glen
- a narrow secluded valley (in the mountains)
- globule
- a small globe or ball
- gluon
- a gauge boson that mediates strong interaction among quarks
- Golden Gate
- a strait in western California that connects the San Francisco Bay with the Pacific Ocean; discovered in 1579 by Sir Francis Drake
- Golfo de Campeche
- a part of the Gulf of Mexico to the west of Yucatan
- Golfo de Mexico
- an arm of the Atlantic to the south of the United States and to the east of Mexico
- Gondwanaland
- a hypothetical continent that (according to plate tectonic theory) broke up later into India and Australia and Africa and South America and Antarctica
- gopher hole
- a hole in the ground made by gophers
- gorge
- a deep ravine (usually with a river running through it)
- Gosainthan
- a mountain in the Himalayas in Tibet (26,290 feet high)
- grain
- a relatively small granular particle of a substance
- Grand Canyon
- the enormous gorge of the Colorado River in northern Arizona
- Grand River
- a river in southern Michigan that flows northwest to empty into Lake Michigan
- Grand Teton
- a mountain peak in northwestern Wyoming; the highest peak in the Teton Range (13,766 feet high)
- granule
- a tiny grain
- graviton
- a gauge boson that mediates the (extremely weak) gravitational interactions between particles
- Great Attractor
- a massive grouping of galaxies in the direction of Centaurus and Hydra whose gravitational attraction is believed to cause deviations in the paths of other galaxies
- Great Australian Bight
- a wide bay of the Indian Ocean in southern Australia; notorious for storms
- Great Barrier Reef
- the largest coral reef in the world; in the Coral Sea off the northeastern coast of Australia
- Great Dividing Range
- a mountain range running along the eastern coast of Australia
- Great Lakes
- a group of five large, interconnected lakes in central North America
- Great Mendenhall Glacier
- a glacier of the Piedmont type near Juneau in Alaska
- Great Plains of North America
- a vast prairie region extending from Alberta and Saskatchewan and Manitoba in Canada south through the west central United States into Texas; formerly inhabited by Native Americans
- Great Rift Valley
- ( geology) a depression in southwestern Asia and eastern Africa; extends from the valley of the Jordan River to Mozambique; marked by geological faults
- Great Salt Lake
- a shallow body of salt water in northwestern Utah
- Great Slave Lake
- a lake in the Northwest Territories in northwestern Canada; drained by the Mackenzie River
- Great Smoky Mountains
- part of the Appalachians between North Carolina and Tennessee
- Green Mountains
- a range of the Appalachian Mountains that extends from south to north through Vermont
- Green River
- a river that rises in western Wyoming and flows southward through Utah to become a tributary of the Colorado River
- Greenland Sea
- part of the Arctic Ocean to the north of Iceland
- greensward
- surface layer of ground containing a mat of grass and grass roots
- greenwood
- woodlands in full leaf
- grinding
- material resulting from the process of grinding
- grot
- a small cave (usually with attractive features)
- ground
- material in the top layer of the surface of the earth in which plants can grow (especially with reference to its quality or use)
- grounds
- dregs consisting of solid particles (especially of coffee) that form a residue
- groundwater level
- underground surface below which the ground is wholly saturated with water
- growler
- a small iceberg or ice floe just large enough to be hazardous for shipping
- growth
- something grown or growing
- Guadalupe Mountains
- a mountain range in southern New Mexico and western Texas; the southern extension of the Sacramento Mountains
- Guaira Falls
- a great waterfall on the border between Brazil and Paraguay
- Guantanamo Bay
- an inlet of the Caribbean Sea; a United States naval station was established on the bay in 1903
- guide fossil
- a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found
- gulf
- a deep wide chasm
- gulf
- an arm of a sea or ocean partly enclosed by land; larger than a bay
- Gulf Coast
- a seashore of the Gulf of Mexico
- Gulf of Aden
- arm of the Indian Ocean at the entrance to the Red Sea
- Gulf of Aegina
- a gulf of the Aegean on the southeastern coast of Greece
- Gulf of Alaska
- a gulf of the Pacific Ocean between the Alaska Peninsula and the Alexander Archipelago
- Gulf of Antalya
- a gulf of the Mediterranean Sea in southwestern Turkey
- Gulf of Aqaba
- a northeastern arm of the Red Sea; between the Sinai Peninsula (Egypt) and Saudi Arabia
- Gulf of Bothnia
- a northern arm of the Baltic Sea; between Sweden and Finland
- Gulf of California
- a gulf to the west of the mainland of Mexico
- Gulf of Carpentaria
- a wide shallow inlet of the Arafura Sea in northern Australia
- Gulf of Finland
- an eastern arm of the Baltic Sea; between Finland and Estonia
- Gulf of Guinea
- a gulf off the southwest coast of Africa
- Gulf of Lepanto
- inlet of the Ionian Sea between central Greece and the Peloponnesus
- Gulf of Martaban
- an arm of the Andaman Sea off southern Myanmar
- Gulf of Ob
- an inlet of the Kara Sea in western Siberia
- Gulf of Oman
- an arm of the Arabian Sea connecting it with the Persian Gulf
- Gulf of Riga
- an inlet of the Baltic Sea between Latvia and Estonia
- Gulf of Saint Lawrence
- an arm of the northwest Atlantic Ocean off the southeastern coast of Canada
- Gulf of Sidra
- wide inlet of the Mediterranean Sea on the north coast of Libya
- Gulf of Suez
- a northwestern arm of the Red Sea linked to the Mediterranean by the Suez Canal
- Gulf of Tehuantepec
- an arm of the Pacific in southern Mexico
- Gulf of Thailand
- an arm of the South China Sea between Indochina and the Malay Peninsula
- Gulf of Venice
- an arm of the Adriatic Sea
- gully
- deep ditch cut by running water (especially after a prolonged downpour)
- gut
- a narrow channel or strait
- guyot
- a seamount of volcanic origin (especially in the Pacific Ocean)
- hadron
- any elementary particle that interacts strongly with other particles
- hail
- many objects thrown forcefully through the air
- hair ball
- a compact mass of hair that forms in the alimentary canal (especially in the stomach of animals as a result of licking fur)
- hammock
- a small natural hill
- Hampton Roads
- a channel in southeastern Virginia through which the Elizabeth River and the James River flow into Chesapeake Bay
- Handies Peak
- a mountain peak in the San Juan Mountains in southwestern Colorado (14,048 feet high)
- hanging wall
- the upper wall of an inclined fault
- Hangzhou Bay
- a bay formed by an inlet of the East China Sea
- head
- the foam or froth that accumulates at the top when you pour an effervescent liquid into a container
- head
- a rounded compact mass
- headstream
- a stream that forms the source of a river
- Heilong Jiang
- an Asian river between China and Russia; flows into the Sea of Okhotsk
- Hercules
- a large constellation in the northern hemisphere between Lyra and Corona Borealis
- Hesperus
- a planet (usually Venus) seen at sunset in the western sky
- heterocycle
- a ring of atoms of more than one kind; especially a ring of carbon atoms containing at least one atom that is not carbon
- high sea
- the open seas of the world outside the territorial waters of any nation
- highland
- elevated (e.g., mountainous) land
- hill
- a local and well-defined elevation of the land
- hillside
- the side or slope of a hill
- Himalaya Mountains
- a mountain range extending 1500 miles on the border between India and Tibet; this range contains the world's highest mountain
- Hindu Kush Mountains
- a mountain range extending to the west of the Himalayas
- Hoek van Holland
- a cape on the southwestern coast of the Netherlands near Rotterdam
- hogback
- a narrow ridge of hills
- hole
- an opening into or through something
- hole
- a depression hollowed out of solid matter
- holler
- a small valley between mountains
- holystone
- a soft sandstone used for scrubbing the decks of a ship
- honeycomb
- a structure of small hexagonal cells constructed from beeswax by bees and used to store honey and larvae
- hornet's nest
- habitation for wasps or hornets
- horsepond
- a pond for watering horses
- Horseshoe Falls
- a part of Niagara Falls in Ontario
- horst
- a ridge of the earth's crust that has been forced upward between two faults and so is higher than the surrounding land
- hot spring
- a natural spring of water at a temperature of 70 F or above
- Housatonic River
- a river that rises in western Massachusetts and flows south through Connecticut to empty into Long Island Sound
- Huascaran
- a mountain in the Andes in Peru (22,205 feet high)
- Hudson Bay
- an inland sea in northern Canada
- Hudson River
- a New York river; flows southward into New York Bay; explored by Henry Hudson early in the 17th century
- Humber
- an estuary in central northeastern England formed by the Ouse River and the Trent River
- hunk
- a large piece of something without definite shape
- Hunter
- a constellation on the equator to the east of Taurus; contains Betelgeuse and Rigel
- hydrogen ion
- a positively charged atom of hydrogen; that is to say, a normal hydrogen atomic nucleus
- hydrosphere
- the watery layer of the earth's surface; includes water vapor
- Hydrus
- a constellation in the southern hemisphere near the south celestial pole
- hyperon
- any baryon that is not a nucleon; unstable particle with mass greater than a neutron
- ice
- the frozen part of a body of water
- ice cap
- a mass of ice and snow that permanently covers a large area of land (e.g., the polar regions or a mountain peak)
- ice field
- a large flat mass of ice (larger than an ice floe) floating at sea
- ice mass
- a large mass of ice
- ice pack
- a large expanse of floating ice
- ice shelf
- ice that is attached to land but projects out to sea
- icefall
- a steep part of a glacier resembling a frozen waterfall
- IJssel river
- a river in the central Netherlands flowing north to the IJsselmeer
- IJsselmeer
- a shallow lake in northwestern Netherlands created in 1932 by building a dam across the entrance to the Zuider Zee
- Illampu
- a mountain peak in the Andes in Bolivia (20,870 feet high)
- Illimani
- a mountain peak in the Andes in Bolivia (21,201 feet high)
- Illinois River
- a river in Illinois that flows southwest to the Mississippi River
- impairer
- an agent that impairs
- incline
- an elevated geological formation
- inclined fault
- a geological fault in which one side is above the other
- Indian Ocean
- the 3rd largest ocean; bounded by Africa on the west, Asia on the north, Australia on the east and merging with the Antarctic Ocean to the south
- Indigirka River
- a river in far eastern Siberia that flows generally northward to the Arctic Ocean
- indirect transmission
- a transmission mechanism in which the infectious agent is transferred to the person by a fomite of vector
- indument
- a covering of fine hairs (or sometimes scales) as on a leaf or insect
- Indus
- a faint constellation in the southern hemisphere near Telescopium and Tucana
- Indus River
- an Asian river that rises in Tibet and flows through northern India and then southwest through Kashmir and Pakistan to the Arabian Sea
- inessential
- anything that is not essential
- infectious agent
- an agent capable of producing infection
- inferior planet
- any of the planets whose orbit lies inside the earth's orbit
- ingrowth
- something that grows inward
- Inland Sea
- an arm of the Pacific Ocean in southern Japan; surrounded by the islands of Honshu and Shikoku and Kyushu and linked to the Sea of Japan by a narrow channel; the chief port is Hiroshima
- inlet
- an arm off of a larger body of water (often between rocky headlands)
- Inside Passage
- a naturally protected waterway from Seattle to Skagway in southeastern Alaska
- inside track
- the inner side of a curved racecourse
- intermediate vector boson
- a gauge boson that mediates weak interactions between particles
- interplanetary dust
- microscopic particles in the interplanetary medium
- interplanetary gas
- a rarefied flow of gas and charged particles (plasma) that stream from the sun and form the solar wind
- interplanetary medium
- interplanetary space including forms of energy and gas and dust
- interstellar medium
- interstellar space including streams of protons moving from the stars
- intrusion
- rock produced by an intrusive process
- Io
- the closest of Jupiter's moons; has active volcanoes
- ion
- a particle that is electrically charged (positive or negative); an atom or molecule or group that has lost or gained one or more electrons
- Ionian Sea
- an arm of the Mediterranean Sea between western Greece and southern Italy
- Irish Sea
- an arm of the North Atlantic between Great Britain and Ireland
- iron filing
- a fragment of iron rubbed off by the use of a file
- Irrawaddy River
- the main river of Myanmar rising in the north and flowing south through the length of Burma to empty into the Andaman Sea
- Irtish River
- an Asian river that rises in the Altai Mountains in northern China and flows generally northwest to become a tributary of the Ob River
- Isere River
- a river in southeastern France; a tributary of the Rhone
- island
- a land mass (smaller than a continent) that is surrounded by water
- Isle of Wight
- an isle and county of southern England in the English Channel
- isle
- a small island
- isthmus
- a relatively narrow strip of land (with water on both sides) connecting two larger land areas
- Isthmus of Corinth
- a narrow isthmus between the Gulf of Corinth and the Saronic Gulf; a canal crosses the isthmus so that navigation is possible between the gulfs
- Isthmus of Kra
- a narrow isthmus linking the Malay Peninsula to the Asian mainland
- Isthmus of Panama
- the isthmus that connects Central America and South America; was formerly called the Isthmus of Darien
- Isthmus of Suez
- the isthmus in northeastern Egypt that connects Africa and Asia
- Isthmus of Tehuantepec
- the narrowest part of southern Mexico is an isthmus between the Bay of Campeche on the north coast and the Gulf of Tehuantepec on the south coast
- J particle
- a neutral meson with a large mass
- jag
- a sharp projection on an edge or surface
- James Bay
- the southern extension of Hudson Bay in Canada between western Quebec and northeastern Ontario
- James River
- a river that rises in North Dakota and flows southward across South Dakota to the Missouri
- James River
- a river in Virginia that flows east into Chesapeake Bay at Hampton Roads
- Japan Trench
- a depression in the floor of the Pacific Ocean to the northeast of Japan that reaches depths of 30,000 feet
- Jebel Musa
- a promontory in northern Morocco opposite the Rock of Gibraltar; one of the Pillars of Hercules
- Jordan River
- a river in Palestine that empties into the Dead Sea; John the Baptist baptized Jesus in the Jordan
- Jovian planet
- any of the four outermost planets in the solar system; much larger than Earth and gaseous in nature (like Jupiter)
- Jupiter
- the largest planet and the 5th from the sun; has many satellites and is one of the brightest objects in the night sky
- K particle
- an unstable meson produced as the result of a high-energy particle collision
- Kamet
- a mountain in the Himalayas in northern India (25,450 feet high)
- Kan River
- a river in southeastern China that flows generally north into the Chang Jiang to the north of Nanchang
- Kanawha River
- a tributary of the Ohio River in West Virginia
- Kansas River
- a river in northeastern Kansas; flows eastward to become a tributary of the Missouri River
- Kara Sea
- part of the Arctic Ocean to the north of Siberia and to the east of the Barents Sea; icebound most of the year
- Karakoram Range
- a mountain range in northern Kashmir; an extension of the Hindu Kush; contains the 2nd highest peak
- Karelian Isthmus
- the isthmus between the Gulf of Finland and Lake Ladoga that connects Finland and Russia
- Kasai River
- a river of southwestern Africa that rises in central Angola and flows east and then north (forming part of the border between Angola and Congo) and continuing northwest through Congo to empty into the Congo River on the border between Congo and Republic of the Congo
- Kattegatt
- a strait of the North Sea between Jutland and Sweden; connects with the North Sea through the Skagerrak
- kettle
- (geology) a hollow (typically filled by a lake) that results from the melting of a mass of ice trapped in glacial deposits
- Khyber Pass
- a mountain pass of great strategic and commercial value in the Hindu Kush on the border between northern Pakistan and western Afghanistan; a route by which invaders entered India
- kidney stone
- a calculus formed in the kidney
- Kissimmee River
- a river of central Florida that flows southward to Lake Okeechobee
- Klamath River
- a river flowing southwest from Oregon through northern California to the Pacific Ocean
- Kodiak Island
- an island off southern Alaska in the Gulf of Alaska; site of the first European settlement in the area which was founded by the Russians in 1784
- kopje
- a small hill rising up from the African veld
- Korea Bay
- an inlet of the Yellow Sea between the Liaodong Peninsula in China and western Korea
- Korean Strait
- a strait between Korea and Japan; connects the East China Sea and the Sea of Japan
- Kuenlun Mountains
- a mountain range in western China that extends eastward from the Indian border for 1000 miles
- Kuiper belt object
- any of many minor planets in the Kuiper belt outside the orbit of Neptune at the edge of the solar system
- Kura River
- a river in western Asia; rises in northeast Turkey and flows to the Caspian Sea
- Labrador Sea
- an arm of the northern Atlantic between Labrador and southern Greenland
- Labrador-Ungava Peninsula
- a peninsular region of eastern Canada between Hudson Bay and the Labrador Sea; contains most of Quebec and the mainland part of Newfoundland and Labrador
- lagoon
- a body of water cut off from a larger body by a reef of sand or coral
- lake
- a body of (usually fresh) water surrounded by land
- Lake Albert Nyanza
- a shallow lake on the border between Uganda and Congo in the Great Rift Valley
- Lake Aral
- a lake to the east of the Caspian Sea lying between Kazakhstan and Uzbekistan
- Lake Baikal
- the largest freshwater lake in Asia or Europe and the deepest lake in the world
- Lake Balaton
- a large shallow lake in western Hungary
- lake bed
- the bottom of a lake
- Lake Canandaigua
- a glacial lake in central New York; one of the Finger Lakes
- Lake Cayuga
- a glacial lake in central New York; the longest of the Finger Lakes
- Lake Chad
- a lake in north central Africa; fed by the Shari river
- Lake Champlain
- a lake in northeastern New York, northwestern Vermont and southern Quebec; site of many battles in the French and Indian War and in the American Revolution and in the War of 1812
- Lake Chelan
- a narrow very deep lake in central Washington in the Cascade Range
- Lake Constance
- a lake in southeastern Germany on the northern side of the Swiss Alps; forms part of the Rhine River
- Lake Edward
- a lake in the Great Rift Valley between Congo and Uganda
- Lake Erie
- the 4th largest of the Great Lakes; it is linked to the Hudson River by the New York State Barge Canal
- Lake Eyre
- a shallow salt lake in south central Australia about 35 feet below sea level; the largest lake in the country and the lowest point on the continent
- Lake Geneva
- a lake between southwestern Switzerland and France that is crossed from east to west by the Rhone
- Lake Huron
- the 2nd largest of the Great Lakes
- Lake Ilmen
- a lake in northwestern Russia; drains through the Volkhov River into Lake Ladoga
- Lake Keuka
- a glacial lake in central New York; one of the Finger Lakes
- Lake Kivu
- a lake in the mountains of central Africa between Congo and Rwanda
- Lake Ladoga
- a lake in northwestern Russia to the north of St. Petersburg; the largest lake in Europe; drains through the Neva River into the Gulf of Finland
- Lake Malawi
- a long lake in southeastern Africa between Tanzania, Mozambique, and Malawi
- Lake Michigan
- the 3rd largest of the Great Lakes; the largest freshwater lake entirely within the United States borders
- Lake Nasser
- lake in Egypt formed by dams built on the Nile River at Aswan
- Lake Okeechobee
- a lake in southeast Florida to the north of the Everglades
- Lake Onega
- lake in northwestern Russia near the border with Finland; second largest lake in Europe
- Lake Ontario
- the smallest of the Great Lakes
- Lake Saint Clair
- a lake between Ontario and Michigan; connected with Lake Huron and Lake Erie
- Lake Superior
- the largest freshwater lake in the world; the deepest of the Great Lakes
- Lake Tahoe
- a lake on the border between Nevada and California to the west of Carson City; a popular resort area
- Lake Tanganyika
- the longest lake in the world in central Africa between Tanzania and Congo in the Great Rift Valley
- Lake Tsana
- a lake in northern Ethiopia; the largest lake in Ethiopia and the source of the Blue Nile
- Lake Vanern
- a lake in southwestern Sweden; the largest lake in Sweden
- Lake Winnipeg
- a lake in southern Canada in Manitoba
- lakefront
- land bordering a lake
- lakeshore
- the shore of a lake
- lambda hyperon
- an electrically neutral baryon with isotopic spin 1
- land mass
- a large continuous extent of land
- landfall
- the seacoast first sighted on a voyage (or flight over water)
- landfill
- a low area that has been filled in
- Laptev Sea
- part of the Arctic Ocean to the north of Siberia (between the Taimyr Peninsula and the New Siberian Islands) that is icebound most of the year
- Large Magellanic Cloud
- the larger of the two Magellanic Clouds visible from the southern hemisphere
- Lascaux
- a cave in southwestern France that contains Paleolithic paintings
- lather
- the foam resulting from excessive sweating (as on a horse)
- lather
- the froth produced by soaps or detergents
- Laudo
- a mountain peak in the Andes in Argentina (20,997 feet high)
- Laurasia
- a hypothetical continent that (according to plate tectonic theory) broke up later into North America and Europe and Asia
- leak
- an accidental hole that allows something (fluid or light etc.) to enter or escape
- ledge
- a projecting ridge on a mountain or submerged under water
- lees
- the sediment from fermentation of an alcoholic beverage
- Lehigh River
- a river in eastern Pennsylvania that flows southeast into the Delaware River
- Lena River
- a Russian river in Siberia; flows northward into the Laptev Sea
- Leo
- a zodiacal constellation in northern hemisphere between Cancer and Virgo
- lepton
- an elementary particle that participates in weak interactions; has a baryon number of 0
- Lepus
- a constellation in the southern hemisphere near Orion and Columba
- lethal agent
- an agent capable of causing death
- Lhotse
- a mountain in the central Himalayas on the border of Tibet and Nepal (27,890 feet high)
- Liaodong Peninsula
- a peninsula in northeastern China that extends into the Yellow Sea, between Bo Hai and Korea Bay
- Libra
- a small faint zodiacal constellation in the southern hemisphere; between Virgo and Scorpius
- lick
- a salt deposit that animals regularly lick
- Ligurian Sea
- an arm of the Mediterranean between northwest Italy and Corsica
- liman
- a long narrow lagoon near the mouth of a river
- liposomal delivery vector
- a transducing vector that uses liposomes to carry the gene of interest
- Little Bear
- a constellation outside the zodiac that rotates around the North Star
- Little Bighorn River
- a river that flows from northern Wyoming into the Bighorn River in southern Montana; site of Custer's Last Stand
- Little Dipper
- a cluster of seven stars in Ursa Minor; at the end of the dipper's handle is Polaris
- Little Missouri River
- a river that rises in northeastern Wyoming and flows through Montana and South Dakota to join the Missouri River in North Dakota
- Little Sioux River
- a river that rises in southwestern Minnesota and flows southwestward to the Missouri River in western Iowa
- Little Wabash River
- a river in eastern Illinois that flows southeastward to the Wabash River
- llano
- an extensive grassy and nearly treeless plain (especially in Latin America)
- Llano Estacado
- a large semiarid plateau forming the southern part of the Great Plains
- Llullaillaco
- a mountain in the Andes on the border between Argentina and Chile (22,057 feet high)
- loadstar
- guiding star; a star that is used as a reference point in navigation or astronomy
- loch
- Scottish word for a lake
- loch
- a long narrow inlet of the sea in Scotland (especially when it is nearly landlocked)
- Loch Achray
- a lake in central Scotland
- Loch Linnhe
- an inlet of the Atlantic Ocean on the western coast of Scotland
- Loch Ness
- a lake in the Scottish highlands; the largest body of fresh water in Great Britain
- Loire River
- the longest French river; rises in the Massif Central and flows north and west to the Atlantic Ocean
- Loire Valley
- the valley of the Loire River where many French wines originated
- long chain
- (chemistry) a relatively long chain of atoms in a molecule
- Long Island Sound
- a sound between Long Island and Connecticut
- lough
- Irish word for a lake
- lough
- a long narrow (nearly landlocked) cove in Ireland
- Lower California
- a mountainous peninsula on northwest Mexico
- lower mantle
- the deeper part of the mantle
- Lower Peninsula
- the part of Michigan between Lake Michigan and Lake Huron
- Lower Tunguska
- a river that arises to the north of Lake Baikal and flows north and west to the Yenisei River
- lowland
- low level country
- lunar crater
- a crater on the Earth's Moon
- Lupus
- a constellation in the southern hemisphere near Centaurus
- Lyra
- a small constellation in the northern hemisphere near Cygnus and Draco; contains the star Vega
- maar
- a flat-bottomed volcanic crater that was formed by an explosion; often filled with water
- Mackenzie River
- a Canadian river; flows into the Beaufort Sea
- mackerel sky
- a sky filled with rows of cirrocumulus or small altocumulus clouds
- Madeira River
- a Brazilian river; tributary of the Amazon River
- Magdalena River
- a river that rises in the Andes mountains in southwestern Colombia and flows generally northward to empty into the Caribbean Sea at Barranquilla
- Magellanic Cloud
- either of two small galaxies orbiting the Milky Way; visible near the south celestial pole
- magnetic dipole
- a dipole with opposing magnetic poles
- magnetic monopole
- a hypothetical particle with a single magnetic pole instead of the usual two
- mainland
- the main land mass of a country or continent; as distinguished from an island or peninsula
- major planet
- (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction
- Makalu
- a mountain in the Himalayas in Nepal (27,790 feet high)
- mantle
- the layer of the earth between the crust and the core
- mare clausum
- (closed sea) a navigable body of water under the jurisdiction of a single nation
- mare liberum
- (free sea) a navigable body of water to which all nations have equal access
- mare nostrum
- (our sea) the Mediterranean to the ancient Romans
- mare's tail
- a long narrow flowing cirrus cloud
- mare
- a dark region of considerable extent on the surface of the moon
- Marmara Denizi
- an inland sea in northwestern Turkey; linked to the Black Sea by the Bosporus and linked to the Aegean by the Dardanelles
- mass
- a body of matter without definite shape
- Massachusetts Bay
- an inlet of the Atlantic Ocean off of eastern Massachusetts extending from Cape Ann on the north to Cape Cod on the south
- massif
- a block of the earth's crust bounded by faults and shifted to form peaks of a mountain range
- Massif Central
- a mountainous plateau in southern France that covers almost one sixth of the country
- mat
- a mass that is densely tangled or interwoven
- matchwood
- fragments of wood
- matrix
- an enclosure within which something originates or develops (from the Latin for womb)
- Matterhorn
- a mountain in the Alps on the border between Switzerland and Italy (14,780 feet high); noted for its distinctive shape
- meander
- a bend or curve, as in a stream or river
- mechanism
- a natural object resembling a machine in structure or function
- Mediterranean Sea
- the largest inland sea; between Europe and Africa and Asia
- Mekong River
- an Asian river; flows through a large delta in southern Vietnam into the South China Sea
- Menai Strait
- a strait in northern Wales between Anglesey Island and the mainland
- Mensa
- a faint constellation in the polar region of the southern hemisphere and containing part of the Large Magellanic Cloud
- Mercedario
- a mountain in the Andes in Argentina (22,210 feet high)
- Mercury
- the smallest planet and the nearest to the sun
- mere
- a small pond of standing water
- Merrimack River
- a river that rises in south central New Hampshire and flows through Concord and Manchester into Massachusetts and empties into the Atlantic Ocean
- mesa
- flat tableland with steep edges
- Mesabi Range
- a range of hills in northeastern Minnesota where rich iron ore deposits were discovered in 1887
- meson
- an elementary particle responsible for the forces in the atomic nucleus; a hadron with a baryon number of 0
- mesosphere
- the atmospheric layer between the stratosphere and the thermosphere
- metal filing
- a fragment of metal rubbed off by the use of a file
- meteor swarm
- a group of meteoroids with similar paths
- meteor
- (astronomy) any of the small solid extraterrestrial bodies that hits the earth's atmosphere
- meteorite
- stony or metallic object that is the remains of a meteoroid that has reached the earth's surface
- Meuse River
- a European river; flows into the North Sea
- micelle
- an electrically charged particle built up from polymeric molecules or ions and occurring in certain colloidal electrolytic solutions like soaps and detergents
- microfossil
- a fossil that must be studied microscopically
- micrometeor
- a meteorite or meteoroid so small that it drifts down to earth without becoming intensely heated in the atmosphere
- Microscopium
- a faint constellation in the southern hemisphere near Sagittarius and Capricornus
- Mid-Atlantic Ridge
- a very long narrow elevation on the ocean floor that runs all the way from Iceland in the North Atlantic to Bouvet Island in the South Atlantic
- mid-water
- the water that is well below the surface but also well above the bottom
- midstream
- the middle of a stream
- Milk River
- a river that rises in the Rockies in northwestern Montana and flows eastward to become a tributary of the Missouri River
- Milky Way Galaxy
- the galaxy containing the solar system; consists of millions of stars that can be seen as a diffuse band of light stretching across the night sky
- millpond
- a pond formed by damming a stream to provide a head of water to turn a mill wheel
- Minamata Bay
- a bay on the west coast of Kyushu; in the 1950s industrial wastes caused mercury poisoning among the Japanese people who ate fish from Minamata Bay
- mineral vein
- a layer of ore between layers of rock
- minor planet
- any of numerous small celestial bodies that move around the sun
- mire
- a soft wet area of low-lying land that sinks underfoot
- Mississippi River
- a major North American river and the chief river of the United States; rises in northern Minnesota and flows southward into the Gulf of Mexico
- Missouri River
- the longest river in the United States; arises in Montana and flows southeastward to become a tributary of the Mississippi at Saint Louis
- Mobile Bay
- a bay of the Gulf of Mexico; fed by the Mobile River
- Mobile River
- a river in southwestern Alabama; flows into Mobile Bay
- Mohawk River
- a river of central New York that flows southeastward to the Hudson River
- Mohorovicic discontinuity
- the boundary between the Earth's crust and the underlying mantle
- molehill
- a mound of earth made by moles while burrowing
- monocline
- a geological formation in which all strata are inclined in the same direction
- Monongahela River
- a river that rises in northern West Virginia and flows north into Pennsylvania where it joins the Allegheny River at Pittsburgh to form the Ohio River
- Monte Bianco
- the highest mountain peak in the Alps; on the border between France and Italy to the south of Geneva (15,781 feet high)
- Monterey Bay
- an inlet of the Pacific Ocean in western California
- moon
- any natural satellite of a planet
- Moon
- the natural satellite of the Earth
- moon
- any object resembling a moon
- moor
- open land usually with peaty soil covered with heather and bracken and moss
- moraine
- accumulated earth and stones deposited by a glacier
- Moray Firth
- an inlet of the North Sea on the northeast coast of Scotland
- Moreau River
- a river that rises in western South Dakota and flows eastward to the Missouri River
- Moreton Bay
- an arm of the Tasman Sea forming a bay to the east of Brisbane
- mother-of-pearl cloud
- a luminous iridescent cloud at a high altitude that may be seen when the sun is a few degrees below the horizon
- motor
- a nonspecific agent that imparts motion
- Mount Adams
- a mountain peak in southwestern Washington in the Cascade Range (12,307 feet high)
- Mount Ararat
- the mountain peak that Noah's ark landed on as the waters of the great flood receded
- Mount Bartle Frere
- the highest mountain peak in Queensland, Australia
- Mount Carmel
- a mountain range in northwestern Israel near the Mediterranean coast
- Mount Communism
- the highest mountain peak in the Pamir Mountains; near the Chinese border in northeastern Tajikistan (24,590 feet high)
- Mount Elbert
- the highest peak in the Rocky Mountains in central Colorado (14,431 feet high)
- Mount Everest
- a mountain in the central Himalayas on the border of Tibet and Nepal; the highest mountain peak in the world (29,028 feet high)
- Mount Godwin Austen
- a mountain peak in the Karakoram Range in northern Kashmir; the 2nd highest peak in the world (28,250 feet high)
- Mount Hubbard
- a mountain peak in southeastern Alaska that is part of the Coast Range (14,950 feet high)
- Mount Kanchenjunga
- a mountain the Himalayas on the border between Nepal and Tibet (28,208 feet high)
- Mount Kilimanjaro
- the highest peak in Africa; located in northeastern Tanzania; 19,340 feet high
- Mount Logan
- a mountain peak in the St. Elias Range in the southwestern Yukon Territory in Canada (19,850 feet high)
- Mount McKinley
- a mountain in south central Alaska; the highest peak in North America (20,300 feet high)
- Mount Olympus
- a mountain peak in northeast Greece near the Aegean coast; believed by ancient Greeks to be the dwelling place of the gods (9,570 feet high)
- Mount Parnassus
- (Greek mythology) a mountain in central Greece where (according to Greek mythology) the Muses lived; known as the mythological home of music and poetry
- Mount Rainier
- a mountain peak in central Washington; highest peak in the Cascade Range; (14,410 feet high)
- Mount Rushmore
- a mountain in the Black Hills of South Dakota; the likenesses of Washington and Jefferson and Lincoln and Roosevelt are carved on it
- Mount Shasta
- a volcanic mountain peak in the Cascade Range in northern California (14,162 feet high)
- Mount Sherman
- a peak in the Rocky Mountains in central Colorado (14,036 feet high)
- Mount Sinai
- a mountain peak in the southern Sinai Peninsula (7,500 feet high); it is believed to be the peak on which Moses received the Ten Commandments
- Mount Whitney
- the highest peak in the Sierra Nevada range in California (14,494 feet high)
- Mount Wilson
- a peak in the San Juan mountains of Colorado (14,246 feet high)
- mount
- a land mass that projects well above its surroundings; higher than a hill
- mountain pass
- the location in a range of mountains of a geological formation that is lower than the surrounding peaks
- mountain peak
- the summit of a mountain
- mountainside
- the side or slope of a mountain
- mouse nest
- where mice bear and raise their young
- mouth
- the point where a stream issues into a larger body of water
- mouth
- an opening that resembles a mouth (as of a cave or a gorge)
- Mozambique Channel
- an arm of the Indian Ocean between Madagascar and southeastern Africa
- mu-meson
- an elementary particle with a negative charge and a half-life of 2 microsecond; decays to electron and neutrino and antineutrino
- mud puddle
- a puddle of mud
- mull
- a term used in Scottish names of promontories
- multiple star
- a system of three or more stars associated by gravity
- Murray River
- a southeast Australian river; flows westward and then south into the Indian Ocean at Adelaide
- Murrumbidgee River
- a river of southeastern Australia; flows westward into the Murray River
- Musca
- a small constellation in the polar region of the southern hemisphere near the Southern Cross and Chamaeleon
- mush
- any soft or soggy mass
- must
- a necessary or essential thing
- mutagen
- any agent (physical or environmental) that can induce a genetic mutation or can increase the rate of mutation
- Muztagh
- a highest mountain peak in the Kunlun Shan in China; near the Indian border (23,891 feet high)
- Nacimiento
- a mountain peak in the Andes in Argentina (21,302 feet high)
- Namoi River
- a river in southeastern Australia that flows generally northwest to join the Darling River
- Nan Ling
- a mountain range in southeastern China running generally east to west
- Nan River
- a river of western Thailand flowing southward to join the Ping River to form the Chao Phraya
- Nanda Devi
- a mountain in the Himalayas in northern India (25,660 feet high)
- Nanga Parbat
- a mountain in the Himalayas in Kashmir (26,660 feet high)
- Nares Deep
- a depression in the floor of the Atlantic Ocean to the north of Haiti and Puerto Rico
- Narragansett Bay
- a deep inlet of the Atlantic Ocean in Rhode Island
- narrow
- a narrow strait connecting two bodies of water
- natural order
- the physical universe considered as an orderly system subject to natural (not human or supernatural) laws
- nature
- the natural physical world including plants and animals and landscapes etc.
- nebula
- an immense cloud of gas (mainly hydrogen) and dust in interstellar space
- nebule
- a small cloud
- neck
- a narrow elongated projecting strip of land
- Neckar River
- a river in Germany; rises in the Black Forest and flows north into the Rhine
- need
- anything that is necessary but lacking
- neighbor
- a nearby object of the same kind
- Neosho River
- a river that rises in eastern Kansas and flows eastward into Oklahoma to become a tributary of the Arkansas River
- Neptune
- a giant planet with a ring of ice particles; the 8th planet from the sun is the most remote of the gas giants
- neritic zone
- the ocean waters from the low tide mark to a depth of about 100 fathoms
- nest
- a structure in which animals lay eggs or give birth to their young
- neutrino
- an elementary, electrically neutral particle with a very small mass
- neutron
- an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus
- neutron star
- a star that has collapsed under its own gravity; it is composed of neutrons
- Neva River
- a river in northwestern Russia flowing generally west into the Gulf of Finland
- neve
- the upper part of a glacier (beyond the limit of perpetual snow) where the snow turns to ice
- New River
- a river in the southeastern United States that flows northward from North Carolina to West Virginia where it empties into the Kanawha River
- New York Bay
- a bay of the North Atlantic; fed by the Hudson River
- Niagara Falls
- waterfall in Canada is the Horseshoe Falls; in the United States it is the American Falls
- Niagara River
- a river flowing from Lake Erie into Lake Ontario; forms boundary between Ontario and New York
- nidus
- a nest in which spiders or insects deposit their eggs
- Niger River
- an African river; flows into the South Atlantic
- Nile River
- the world's longest river (4150 miles); flows northward through eastern Africa into the Mediterranean; the Nile River valley in Egypt was the site of the world's first great civilization
- nimbus
- a dark grey cloud bearing rain
- Niobrara River
- a tributary of the Missouri River
- nodule
- (mineralogy) a small rounded lump of mineral substance (usually harder than the surrounding rock or sediment)
- Norma
- a small constellation in the southern hemisphere near Lupus and Ara in the Milky Way
- North America
- a continent (the third largest) in the western hemisphere connected to South America by the Isthmus of Panama
- North Atlantic
- that part of the Atlantic Ocean to the north of the equator
- North Channel
- a strait between Northern Ireland and Scotland that connects the Atlantic Ocean and the Irish Sea
- North Pacific
- that part of the Pacific Ocean to the north of the equator
- North Peak
- 19,370 feet high
- North Platte River
- a river that rises in northern Colorado and flows northward into Wyoming and then eastward and southeastward through Nebraska where it joins the South Platte to form the Platte River
- North Sea
- an arm of the North Atlantic between the British Isles and Scandinavia; oil was discovered under the North Sea in 1970
- North Star
- the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it
- Northern Cross
- a cluster of 5 bright stars forming a cross in the constellation Cygnus
- Norwegian Sea
- the part of the Atlantic that lies off the Norwegian coast to the north of the North Sea
- nova
- a star that ejects some of its material in the form of a cloud and becomes more luminous in the process
- nub
- a small piece
- nubbin
- a small nub (especially an undeveloped fruit or ear of corn)
- nucleon
- a constituent (proton or neutron) of an atomic nucleus
- nucleus
- the positively charged dense center of an atom
- nucleus
- (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail
- nugget
- a solid lump of a precious metal (especially gold) as found in the earth
- nullah
- a ravine or gully in southern Asia
- Nuptse
- a mountain in the central Himalayas on the border of Tibet and Nepal (25,726 feet high)
- Ob River
- a major river of western Siberia; flows generally northward and westward to the Gulf of Ob and the Kara Sea
- obliterator
- an eliminator that does away with all traces
- ocean
- a large body of water constituting a principal part of the hydrosphere
- oceanfront
- land bordering an ocean
- Octans
- the constellation that includes the southern celestial pole
- Oder River
- a European river; flows into the Baltic Sea
- offing
- the part of the sea that can be seen from the shore and is beyond the anchoring area
- Ohio River
- a river that is formed in western Pennsylvania and flows westward to become a tributary of the Mississippi River
- oil-water interface
- an interface forming the boundary between the non-miscible liquids oil and water
- Ojos del Salado
- a mountain in the Andes on the border between Argentina and Chile (22,572 feet high)
- Okefenokee Swamp
- a large swampy area of northeast Florida and southeast Georgia
- Old Faithful
- a geyser in Yellowstone National Park that erupts for about 4 minutes about every 65 minutes
- Olduvai Gorge
- a gorge in northeastern Tanzania where anthropologists have found some of the earliest human remains
- Omega Centauri
- a global cluster in the constellation Centaurus
- open chain
- a chain of atoms in a molecule whose ends are not joined to form a ring
- Ophiuchus
- a large constellation in the equatorial region between Hercules and Scorpius
- Orange River
- a river in South Africa that flows generally westward to the Atlantic Ocean
- ore bed
- a stratum of ore
- Orinoco River
- a South American river 1,500 miles long; flows into the South Atlantic
- Osage River
- a river in Missouri that is a tributary of the Missouri River
- Osaka Bay
- a bay of the western Pacific in southern Honshu
- Ottawa river
- a river in southeastern Canada that flows along the boundary between Quebec and Ontario to the Saint Lawrence River near Montreal
- Ouachita River
- a river that rises in western Arkansas and flows southeast into eastern Louisiana to become a tributary of the Red River
- Ouse River
- a river in northeastern England that flows generally southeastward to join the Trent River and form the Humber
- outcrop
- the part of a rock formation that appears above the surface of the surrounding land
- outer planet
- (astronomy) a major planet whose orbit is outside the asteroid belt (Jupiter, Saturn, Uranus, Neptune, Pluto)
- outthrust
- an outcropping of rock that extends outward
- overburden
- the surface soil that must be moved away to get at coal seams and mineral deposits
- overthrust fault
- a geological fault in which the upper side appears to have been pushed upward by compression
- oxbow
- a U-shaped curve in a stream
- oxbow
- the land inside an oxbow bend in a river
- oxbow lake
- a crescent-shaped lake (often temporary) that is formed when a meander of a river is cut off from the main channel
- Ozark Mountains
- an area of low mountains in northwestern Arkansas and southeastern Missouri and northeastern Oklahoma
- ozone hole
- an area of the ozone layer (near the poles) that is seasonally depleted of ozone
- ozone layer
- a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun
- Pacific Coast
- a coast of the Pacific Ocean
- Pacific Ocean
- the largest ocean in the world
- Pallas
- a large asteroid; the second asteroid to be discovered
- pallasite
- a meteorite composed principally of olivine and metallic iron
- Pamir Mountains
- a mountain range in central Asia that is centered in Tajikistan but extends into Kyrgyzstan and Afghanistan and Pakistan and western China
- Pangaea
- (plate tectonics) a hypothetical continent including all the landmass of the earth prior to the Triassic period when it split into Laurasia and Gondwanaland
- Para River
- an estuary in northern Brazil into which the Tocantins River flows
- Parana River
- a South American river; tributary of Rio de la Plata
- paring
- a thin fragment or slice (especially of wood) that has been shaved from something
- Parnahiba
- a river in northeastern Brazil that flows generally northward to the Atlantic Ocean
- part
- a portion of a natural object
- particle
- a body having finite mass and internal structure but negligible dimensions
- Paulo Afonso Falls
- a major waterfall in northeastern Brazil
- Pavo
- a small constellation near the South Pole between Tucana and Ara
- Pearl River
- a river in Mississippi that flows southward to the Gulf of Mexico
- pebble
- a small smooth rounded rock
- Pecos River
- a tributary of the Rio Grande that flows southeastward from New Mexico through western Texas
- Pee Dee River
- a river that flows through central North Carolina and northeastern South Carolina to the Atlantic Ocean
- Pegasus
- a constellation in the northern hemisphere near Andromeda and Pisces
- peneplain
- a more or less level land surface representing an advanced stage of erosion undisturbed by crustal movements
- peninsula
- a large mass of land projecting into a body of water
- Penobscot Bay
- an inlet of the Atlantic in eastern Maine
- Penobscot River
- a river in central Maine flowing into Penobscot Bay
- Perejil
- a small uninhabited Mediterranean islet claimed by both Morocco and Spain
- perforation
- a hole made in something
- permafrost
- ground that is permanently frozen
- Perseus
- a conspicuous constellation in the northern hemisphere; between Auriga and Cassiopeia and crossed by the Milky Way
- Persian Gulf
- a shallow arm of the Arabian Sea between Iran and the Arabian peninsula; the Persian Gulf oil fields are among the most productive in the world
- petrifaction
- a rock created by petrifaction; an organic object infiltrated with mineral matter and preserved in its original form
- Phobos
- the larger of the two satellites of Mars
- Phoenix
- a constellation in the southern hemisphere near Tucana and Sculptor
- Phosphorus
- a planet (usually Venus) seen just before sunrise in the eastern sky
- photoelectron
- an electron that is emitted from an atom or molecule by an incident photon
- photon
- a quantum of electromagnetic radiation; an elementary particle that is its own antiparticle
- photosphere
- the intensely luminous surface of a star (especially the sun)
- pi-meson
- a meson involved in holding the nucleus together; produced as the result of high-energy particle collision
- Pictor
- a constellation in the southern hemisphere near Dorado and Columba
- piedmont
- a gentle slope leading from the base of a mountain to a region of flat land
- Piedmont type of glacier
- a type of glaciation characteristic of Alaska; large valley glaciers meet to form an almost stagnant sheet of ice
- Pike's Peak
- a mountain peak in the Rockies in central Colorado (14,109 feet high)
- Pillars of Hercules
- the two promontories at the eastern end of the Strait of Gibraltar; according to legend they were formed by Hercules
- pinetum
- an area planted with pine trees or related conifers
- Ping River
- a river in western Thailand; a major tributary of the Chao Phraya
- Pisces
- a large faint zodiacal constellation; between Aquarius and Aries
- Pissis
- a mountain in the Andes in Argentina (22,241 feet high)
- placer
- an alluvial deposit that contains particles of some valuable mineral
- plage
- the beach at a seaside resort
- planet
- any celestial body (other than comets or satellites) that revolves around a star
- planetary nebula
- a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star
- planetesimal
- one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system
- plasmid DNA
- a small cellular inclusion consisting of a ring of DNA that is not in a chromosome but is capable of autonomous replication
- plateau
- a relatively flat highland
- Platte River
- a river in Nebraska that flows eastward to become a tributary of the Missouri River
- Pleiades
- a star cluster in the constellation Taurus
- Pluto
- a large asteroid that was once thought to be the farthest known planet from the sun; it has an elliptical orbit
- Po Hai
- an inlet of the Yellow Sea, on the coast of Eastern China
- Po River
- a European river; flows into the Adriatic Sea
- Pobedy Peak
- a mountain peak in the Tien Shan mountains in northern India (24,406 feet high)
- point
- a promontory extending out into a large body of water
- polar glacier
- a glacier near the Arctic or Antarctic poles
- polder
- low-lying land that has been reclaimed and is protected by dikes (especially in the Netherlands)
- Pollux
- the brightest star in Gemini; close to Castor
- polynya
- a stretch of open water surrounded by ice (especially in Arctic seas)
- pond
- a small lake
- pool
- a small body of standing water (rainwater) or other liquid
- Potomac River
- a river in the east central United States; rises in West Virginia in the Appalachian Mountains and flows eastward, forming the boundary between Maryland and Virginia, to the Chesapeake Bay
- Poyang
- a lake in central China that is connected to the Chang Jiang by a canal
- precipice
- a very steep cliff
- primary
- (astronomy) a celestial body (especially a star) relative to other objects in orbit around it
- prion
- (microbiology) an infectious protein particle similar to a virus but lacking nucleic acid; thought to be the agent responsible for scrapie and other degenerative diseases of the nervous system
- Procyon
- the brightest star in Canis Minor
- protein molecule
- any large molecule containing chains of amino acids linked by peptide bonds
- proton
- a stable particle with positive charge equal to the negative charge of an electron
- Proxima Centauri
- the nearest star to the sun; distance: 4.3 light years
- Prudhoe Bay
- a bay on the northern coast of Alaska where oil was discovered in 1968
- pruning
- something that has been pruned off of a plant
- ptyalith
- calculus in a salivary gland
- Puget Sound
- an inlet of the North Pacific in northwestern Washington State
- pulsar
- a degenerate neutron star; small and extremely dense; rotates very fast and emits regular pulses of polarized radiation
- Puppis
- a constellation in the southern hemisphere between Vela and Canis Major that shaped like the stern of a boat
- Purus River
- a Brazilian river; tributary of the Amazon River
- Pyrenees
- a chain of mountains between France and Spain
- Pyxis
- a constellation in the southern hemisphere near Puppis and Antlia
- Quaoar
- a planetoid discovered in 2002
- quark
- (physics) hypothetical truly fundamental particle in mesons and baryons; there are supposed to be six flavors of quarks (and their antiquarks), which come in pairs; each has an electric charge of +2/3 or -1/3
- quasar
- a starlike object that may send out radio waves and other forms of energy; many have large red shifts
- Queen Charlotte Sound
- an inlet of the Pacific Ocean off the coast of British Columbia
- quicksand
- a pit filled with loose wet sand into which objects are sucked down
- rabbit burrow
- a hole in the ground as a nest made by wild rabbits
- rabbit warren
- a series of connected underground tunnels occupied by rabbits
- radiator
- any object that radiates energy
- radio source
- an object that radiates radio waves
- rainbow
- an arc of colored light in the sky caused by refraction of the sun's rays by rain
- Rakaposhi
- a mountain peak in the Karakoram Range in northern Kashmir (25,560 feet high)
- rangeland
- land suitable for grazing livestock
- rapid
- a part of a river where the current is very fast
- Rappahannock River
- a river that flows across eastern Virginia into the Tidewater region
- rathole
- a hole (as in the wall of a building) made by rats
- ravine
- a deep narrow steep-sided valley (especially one formed by running water)
- red dwarf
- a small, old, relatively cool star; approximately 100 times the mass of Jupiter
- red giant
- a large, old, luminous star; has a relatively low surface temperature and a diameter large relative to the sun
- Red Planet
- a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye; minerals rich in iron cover its surface and are responsible for its characteristic color
- Red River
- a tributary of the Mississippi River that flows eastward from Texas along the southern boundary of Oklahoma and through Louisiana
- Red Sea
- a long arm of the Indian Ocean between northeast Africa and Arabia; linked to the Mediterranean at the north end by the Suez Canal
- reef
- a submerged ridge of rock or coral near the surface of the water
- Regulus
- the brightest star in Leo
- relaxer
- any agent that produces relaxation
- relict
- geological feature that is a remnant of a pre-existing formation after other parts have disappeared
- remains
- any object that is left unused or still extant
- rent
- an opening made forcibly as by pulling apart
- represser
- an agent that represses
- Republican River
- a tributary of the Kansas River that flows from eastern Colorado eastward through Nebraska and Kansas
- reservoir
- anything (a person or animal or plant or substance) in which an infectious agent normally lives and multiplies
- restriction fragment
- the fragment of DNA that is produced by cleaving DNA with a restriction enzyme
- retardant
- any agent that retards or delays or hinders
- Reticulum
- a small constellation in the southern hemisphere near Dorado and Hydrus
- Rhine River
- a major European river carrying more traffic than any other river in the world; flows into the North Sea
- Rhodope Mountains
- a mountain range in the Balkan peninsula in southeastern Europe; extends along the border between Greece and Bulgaria
- Rhone River
- a major French river; flows into the Mediterranean near Marseilles
- ribbon
- any long object resembling a thin line
- ridge
- a long narrow natural elevation or striation
- ridge
- a long narrow natural elevation on the floor of the ocean
- ridge
- a long narrow range of hills
- rift
- a narrow fissure in rock
- rift
- a gap between cloud masses
- rift valley
- a valley with steep sides; formed by a rift in the earth's crust
- rill
- a small channel (as one formed by soil erosion)
- rill
- a small stream
- Rio de la Plata
- an estuary between Argentina and Uruguay
- Rio Grande
- a North American river; boundary between the United States and Mexico; flows into Gulf of Mexico
- riparian forest
- woodlands along the banks of stream or river
- ripple mark
- one of a series of small ridges produced in sand by water currents or by wind
- river
- a large natural stream of water (larger than a creek)
- River Acheron
- (Greek mythology) a river in Hades across which the souls of the dead were carried by Charon
- River Adige
- a river in northern Italy that flows southeast into the Adriatic Sea
- River Avon
- a river in southwestern England rising in Gloucestershire and flowing through Bristol to empty into the estuary of the Severn
- river bottom
- a channel occupied (or formerly occupied) by a river
- river boulder
- a boulder that has been carried by a river to a place remote from its place of origin
- River Cocytus
- (Greek mythology) a river in Hades that was said to be a tributary of the Acheron
- River Lethe
- (Greek mythology) a river in Hades; the souls of the dead had to drink from it, which made them forget all they had done and suffered when they were alive
- River Severn
- a river in England and Wales flowing into the Bristol Channel; the longest river in Great Britain
- River Styx
- (Greek mythology) a river in Hades across which Charon carried dead souls
- River Thames
- the longest river in England; flows eastward through London to the North Sea
- River Trent
- a river in central England that flows generally northeastward to join with the Ouse River and form the Humber
- River Tyne
- a river in northern England that flows east to the North Sea
- riverbank
- the bank of a river
- rock
- a lump or mass of hard consolidated mineral matter
- Rocky Mountains
- the chief mountain range of western North America; extends from British Columbia to northern New Mexico; forms the continental divide
- roof
- the inner top surface of a covered area or hollow space
- Ross Sea
- an arm of the southern Pacific Ocean in Antarctica
- round
- the course along which communications spread
- row
- a long continuous strip (usually running horizontally)
- Ruhr River
- a tributary of the Rhine
- Russell's body
- an inclusion body found in plasma cells in cases of cancer
- Russian River
- a river in northern California
- Saale River
- a river that rises in central Germany and flows north to join the Elbe River
- Sabine River
- a river in eastern Texas that flows south into the Gulf of Mexico
- Sacramento Mountains
- mountain range in New Mexico to the east of the Rio Grande
- Sacramento River
- a river in northern California rising near Mount Shasta and flowing south to the San Francisco Bay
- saddle
- a pass or ridge that slopes gently between two peaks (is shaped like a saddle)
- Sagitta
- a small constellation in the northern hemisphere between Cygnus and Aquila and crossed by the Milky Way
- Sagittarius
- a large zodiacal constellation in the southern hemisphere; between Scorpius and Capricornus
- Saint Francis River
- a tributary of the Mississippi River that rises in Missouri and flows southeastward through Arkansas
- Saint John River
- a river that rises in Maine and flows northeastward through New Brunswick to empty into the Bay of Fundy
- Saint Johns River
- a river in northeastern Florida that flows northward to Jacksonville and then eastward to empty into the Atlantic Ocean
- Saint Lawrence River
- a North American river; flows into the Gulf of Saint Lawrence and the North Atlantic
- Sajama
- a mountain peak in the Andes in Bolivia (21,391 feet high)
- salivary calculus
- a stone formed in the salivary gland
- Salmon River
- a tributary of the Snake River in Idaho
- salt flat
- a flat expanse of salt left by the evaporation of a body of salt water
- salt marsh
- low-lying wet land that is frequently flooded with saltwater
- Salton Sea
- a saltwater lake in southeastern California
- saltpan
- a shallow basin in a desert region; contains salt and gypsum that was deposited by an evaporated salt lake
- Sambre River
- a river in western Europe that rises in northern France and flows generally east into Belgium where it joins the Meuse at Namur
- sample
- all or part of a natural object that is collected and preserved as an example of its class
- San Andreas Fault
- a major geological fault in California; runs from San Diego to San Francisco; the source of serious earthquakes
- San Diego Bay
- a bay of the Pacific in southern California
- San Fernando Valley
- a fertile valley in southern California to the north of Los Angeles; includes many residential communities
- San Francisco Bay
- a bay of the Pacific in western California
- San Joaquin River
- a river in central California that rises in the Sierra Nevada and flows northwest to form a large delta with the Sacramento River
- San Joaquin Valley
- a vast valley in central California known for its rich farmland
- San Juan Hill
- a hill in eastern Cuba (near Santiago de Cuba) that was captured during the Spanish-American War
- San Juan Mountains
- a mountain range in southwestern Colorado that is part of the Rocky Mountains
- sand bar
- a bar of sand
- sandbank
- a submerged bank of sand near a shore or in a river; can be exposed at low tide
- sandpit
- a large pit in sandy ground from which sand is dug
- sanitary landfill
- a low area where waste is buried between layers of earth
- Sao Francisco
- a river in eastern Brazil flowing into the Atlantic Ocean
- Saone River
- a river in eastern France; rises in Lorraine and flows south to become the chief tributary of the Rhone
- Sargasso Sea
- a vast area of the North Atlantic from the West Indies to the Azores that is dense with gulfweed
- satellite
- any celestial body orbiting around a planet or star
- satisfier
- any agent capable of producing satisfaction
- Saturn
- a giant planet that is surrounded by three planar concentric rings of ice particles; the 6th planet from the sun
- Savannah River
- a river in South Carolina that flows southeast to the Atlantic
- sawpit
- a pit over which lumber is positioned to be sawed by two men with a long two-handed saw
- Sayan Mountains
- a range of mountains in southern Siberia to the west of Lake Baikal; contain important mineral deposits
- scablands
- (geology) flat elevated land with poor soil and little vegetation that is scarred by dry channels of glacial origin (especially in eastern Washington)
- Scheldt River
- a river that rises in France and flows northeast across Belgium and empties into the North Sea
- scintilla
- a sparkling glittering particle
- Scorpius
- a large zodiacal constellation between Libra and Sagittarius
- scraping
- (usually plural) a fragment scraped off of something and collected
- scree
- a sloping mass of loose rocks at the base of a cliff
- Sculptor
- a faint constellation in the southern hemisphere near Phoenix and Cetus
- scurf
- (botany) a covering that resembles scales or bran that covers some plant parts
- sea
- a division of an ocean or a large body of salt water partially enclosed by land
- Sea of Azoff
- a bay of the Black Sea between Russia and the Ukraine
- Sea of Japan
- an arm of the Pacific bordered by Japan, Korea, North Korea, and Russia
- Sea of Okhotsk
- an arm of the Pacific to the east of Asia
- seaboard
- the shore of a sea or ocean regarded as a resort
- seamount
- an underwater mountain rising above the ocean floor
- section
- a very thin slice (of tissue or mineral or other substance) for examination under a microscope
- Sedna
- a planetoid of rock and ice about three-quarters the size of Pluto discovered in 2003; the most distant object known to orbit around the sun
- segment
- one of the parts into which something naturally divides
- seif dune
- a long and tall sand dune with a sharp crest; common in the Sahara
- Seine River
- a French river that flows through the heart of Paris and then northward into the English Channel
- Selkirk Mountains
- a range of the Rocky Mountains in southeastern British Columbia
- Seneca Lake
- a glacial lake in central New York; the largest of the Finger Lakes
- Serpens
- a constellation in the equatorial region of the northern hemisphere near Ophiuchus and Corona Borealis
- seven seas
- an informal expression for all of the oceans of the world
- Severn River
- a river in Ontario that flows northeast into Hudson Bay
- Seyhan River
- a Turkish river flowing south southwest into the Mediterranean
- shag
- a matted tangle of hair or fiber
- shallow
- a stretch of shallow water
- sheet
- any broad thin expanse or surface
- shell
- a rigid covering that envelops an object
- Shenandoah River
- a river of northern Virginia that empties into the Potomac at Harpers Ferry
- Shenandoah Valley
- a large valley between the Allegheny Mountains and the Blue Ridge Mountains in northern Virginia; site of numerous battles during the American Civil War
- Sherwood Forest
- an ancient forest in central England; formerly a royal hunting ground; said to be the home of Robin Hood and his merry band
- shiner
- something that shines (with emitted or reflected light)
- shoal
- a sandbank in a stretch of water that is visible at low tide
- shore
- the land along the edge of a body of water
- shore boulder
- a boulder found on a shore remote from its place of origin
- shoreline
- a boundary line between land and water
- shortener
- any agent that shortens
- siderite
- a meteorite consisting principally of nickel and iron
- sierra
- a range of mountains (usually with jagged peaks and irregular outline)
- Sierra Madre Occidental
- a mountain range in northwestern Mexico that runs south from Arizona parallel to the Pacific coastline
- Sierra Madre Oriental
- a mountain range in northeastern Mexico the runs parallel to the coastline of the Gulf of Mexico
- Sierra Nevada
- a mountain range in southern Spain along the Mediterranean coast to the east of Granada
- Sierra Nevada Mountains
- a mountain range in eastern California; contains Mount Whitney
- sill
- (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock
- silva
- the forest trees growing in a country or region
- sink
- a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
- Skagens Odde
- a cape on the northernmost tip of Jutland between the Skagerrak and the Kattegatt
- Skagerrak
- a broad strait of the North Sea between Jutland and Norway
- ski slope
- a snow-covered slope for skiing
- skim
- a thin layer covering the surface of a liquid
- sky
- the atmosphere and outer space as viewed from the earth
- slack
- a stretch of water without current or movement
- slash
- an open tract of land in a forest that is strewn with debris from logging (or fire or wind)
- slice
- a thin flat piece cut off of some object
- slit
- a narrow fissure
- sliver
- a small thin sharp bit or wood or glass or metal
- slot
- the trail of an animal (especially a deer)
- slough
- any outer covering that can be shed or cast off (such as the cast-off skin of a snake)
- slough
- a stagnant swamp (especially as part of a bayou)
- slough
- a hollow filled with mud
- Small Magellanic Cloud
- the smaller of the two Magellanic Clouds visible from the southern hemisphere
- Snake
- a long faint constellation in the southern hemisphere near the equator stretching between Virgo and Cancer
- Snake River
- a tributary of the Columbia River that rises in Wyoming and flows westward; discovered in 1805 by the Lewis and Clark Expedition
- snowcap
- a covering of snow (as on a mountain peak)
- snowdrift
- a mass of snow heaped up by the wind
- snowfield
- a permanent wide expanse of snow
- soap bubble
- a bubble formed by a thin soap film
- solar system
- the sun with the celestial bodies that revolve around it in its gravitational field
- Solent
- a strait of the English Channel between the coast of Hampshire and the Isle of Wight
- Solway Firth
- a large firth on the west coast of Britain between England and Scotland
- sound
- a large ocean inlet or deep bay
- sound
- a narrow channel of the sea joining two larger bodies of water
- South America
- a continent in the western hemisphere connected to North America by the Isthmus of Panama
- South Atlantic
- that part of the Atlantic Ocean to the south of the equator
- South China Sea
- a tropical arm of the Pacific Ocean near southeastern Asia subject to frequent typhoons
- South Pacific
- that part of the Pacific Ocean to the south of the equator
- South Platte River
- a tributary of the Platte River
- South Sea
- any sea to the south of the equator (but especially the South Pacific)
- South Sea Islands
- any islands in the southern or southwestern of central parts of the Pacific Ocean
- spall
- a fragment broken off from the edge or face of stone or ore and having at least one thin edge
- spark
- a small fragment of a burning substance thrown out by burning material or by friction
- Spica
- the brightest star in Virgo
- spit
- a narrow strip of land that juts out into the sea
- splint
- a thin sliver of wood
- split
- a lengthwise crack in wood
- spoor
- the trail left by a person or an animal; what the hunter follows in pursuing game
- spume
- foam or froth on the sea
- squark
- a quark with an electric charge of -1/3 and a mass 988 times that of an electron and a strangeness of -1
- St. Elias Mountains
- a range of mountains between Alaska and the Yukon territory
- stalactite
- a cylinder of calcium carbonate hanging from the roof of a limestone cave
- stalagmite
- a cylinder of calcium carbonate projecting upward from the floor of a limestone cave
- star
- (astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior
- star
- any celestial body visible (as a point of light) from the Earth at night
- starlet
- a small star
- steep
- a steep place (as on a hill)
- steppe
- extensive plain without trees (associated with eastern Russia and Siberia)
- stepping stone
- a stone in a marsh or shallow water that can be stepped on in crossing
- steps
- the course along which a person has walked or is walking in
- Stony Tunguska
- a river in Siberia that flows northwest to become a tributary of the Yenisei River
- storm cloud
- a heavy dark cloud presaging rain or a storm
- straight chain
- an open chain of atoms with no side chains
- Strait of Calais
- the strait between the English Channel and the North Sea; shortest distance between England and the European continent
- Strait of Georgia
- the strait separating Vancouver Island from the Canadian mainland
- Strait of Gibraltar
- the strait between Spain and Africa
- Strait of Hormuz
- a strategically important strait linking the Persian Gulf and the Gulf of Oman
- Strait of Magellan
- the strait separating South America from Tierra del Fuego and other islands to the south of the continent; discovered by Ferdinand Magellan in 1520; an important route around South America before the Panama Canal was built
- Strait of Malacca
- the strait between the Malay Peninsula and Sumatra; it connects the Pacific Ocean to the east with the Indian Ocean to the west and is an important shipping lane
- Strait of Messina
- the strait separating Sicily from the tip of Italy
- strand
- a poetic term for a shore (as the area periodically covered and uncovered by the tides)
- strange particle
- an elementary particle with non-zero strangeness
- stratosphere
- the atmospheric layer between the troposphere and the mesosphere
- stratus
- a large dark low cloud
- stream
- a natural body of running water flowing on or under the earth
- stressor
- any agent that causes stress to an organism
- stretch
- a large and unbroken expanse or distance
- strike-slip fault
- a geological fault in which one of the adjacent surfaces appears to have moved horizontally
- strip
- a relatively long narrow piece of something
- stub
- a short piece remaining on a trunk or stem where a branch is lost
- subcontinent
- a large and distinctive landmass (as India or Greenland) that is a distinct part of some continent
- Sun
- the star that is the source of light and heat for the planets in the solar system
- sun
- any star around which a planetary system revolves
- Sun River
- a river in western Montana that flows south and east to join the Missouri River
- supergiant
- an extremely bright star of very large diameter and low density
- superior planet
- any of the planets whose orbit lies outside the earth's orbit
- supernatant
- the clear liquid that lies above a sediment or precipitate
- supernova
- a star that explodes and becomes extremely luminous in the process
- superstring
- a hypothetical particle that is the elementary particle in a theory of space-time
- Suriname River
- a river in Suriname that flows northward to the Atlantic
- Susquehanna River
- a river in the northeastern United States that rises in New York and flows southward through Pennsylvania and Maryland into Chesapeake Bay
- swale
- a low area (especially a marshy area between ridges)
- swamp
- low land that is seasonally flooded; has more woody plants than a marsh and better drainage than a bog
- swell
- a rounded elevation (especially one on an ocean floor)
- swimming hole
- a small body of water (usually in a creek) that is deep enough to use for swimming
- Taconic Mountains
- a range of the Appalachian Mountains along the eastern border of New York with Connecticut, Massachusetts, and Vermont
- Tagus River
- a European river; flows into the North Atlantic
- Takakkaw
- a waterfall in southeastern British Columbia; the highest waterfall in Canada (1250 feet high)
- Tallapoosa River
- river that rises in northwestern Georgia and flows southwest through central Alabama to join the Coosa River near Montgomery and form the Alabama River
- Tampa Bay
- an arm of the Gulf of Mexico in west central Florida
- tangle
- a twisted and tangled mass that is highly interwoven
- tar pit
- a natural accumulation of bitumens at the surface of the earth; often acts as a trap for animals whose bones are thus preserved
- tarn
- a mountain lake (especially one formed by glaciers)
- Tasman Sea
- an arm of the southern Pacific Ocean between southeastern Australia and New Zealand
- tau-minus particle
- a lepton of very great mass
- Taurus
- a zodiacal constellation in the northern hemisphere near Orion; between Aries and Gemini
- Telescopium
- a small constellation in the southern hemisphere near Ara
- Tennessee River
- a river formed by the confluence of two other rivers near Knoxville; it follows a U-shaped course to become a tributary of the Ohio River in western Kentucky
- tent
- a web that resembles a tent or carpet
- teratogen
- any agent that interferes with normal embryonic development: alcohol or thalidomide or X-rays or rubella are examples
- terrestrial planet
- a planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system
- territorial waters
- the waters surrounding a nation and its territories over which that nation exercises sovereign jurisdiction
- Teton Range
- a mountain range in northwest Wyoming; contains the Grand Teton
- Tevere
- a river of central Italy; flows through Rome to the Tyrrhenian Sea
- the Alps
- a large mountain system in south-central Europe; scenic beauty and winter sports make them a popular tourist attraction
- thermion
- an electrically charged particle (electron or ion) emitted by a substance at a high temperature
- thermosphere
- the atmospheric layer between the mesosphere and the exosphere
- thunderhead
- a rounded projecting mass of a cumulus cloud with shining edges; often appears before a thunderstorm
- tidal basin
- a basin that is full of water at high tide
- tidal river
- a stream in which the effects of the tide extend far upstream
- tideland
- land near the sea that is overflowed by the tide
- tidewater
- low-lying coastal land drained by tidal streams
- tideway
- a channel in which a tidal current runs
- Tigris River
- an Asian river; a tributary of the Euphrates River
- Timor Sea
- an arm of the eastern Indian Ocean between Timor and northern Australia
- Tirich Mir
- a mountain in the Hindu Kush in Pakistan (25,230 feet high)
- Titan
- the largest of the satellites of Saturn; has a hazy nitrogen atmosphere
- Tocantins River
- a river in eastern Brazil that flows generally north to the Para River
- Tombigbee River
- a river that rises in northeastern Mississippi and flows southward through western Alabama to join the Alabama River and form the Mobile River
- top quark
- a hypothetical quark with a charge of +2/3 and a mass more than 100,000 times that of an electron
- tor
- a high rocky hill
- tor
- a prominent rock or pile of rocks on a hill
- Torres Strait
- a strait between northeastern Australia and southern New Guinea that connects the Coral Sea with the Arafura Sea
- trail
- a track or mark left by something that has passed
- transmission mechanism
- any mechanism whereby an infectious agent is spread from a reservoir to a human being
- transmitter
- any agent (person or animal or microorganism) that carries and transmits a disease
- Transylvanian Alps
- a range of the southern Carpathian Mountains extending across central Romania
- Trapezium
- a multiple star in the constellation of Orion
- tree farm
- a forest (or part of a forest) where trees are grown for commercial use
- Triangulum
- a small northern constellation near Perseus between Andromeda and Aries
- Triangulum Australe
- a small bright constellation in the polar region of the southern hemisphere near Circinus and Apus
- Trinity River
- a river in eastern Texas that is formed near Dallas and flows generally southeastward to Galveston Bay
- Triton
- the largest moon of Neptune
- Trondheim Fjord
- a long narrow inlet of the Norwegian Sea
- tropopause
- the region of discontinuity between the troposphere and the stratosphere
- troposphere
- the lowest atmospheric layer; from 4 to 11 miles high (depending on latitude)
- trough
- a narrow depression (as in the earth or between ocean waves or in the ocean bed)
- Tucana
- a large faint constellation in the southern hemisphere containing most of the Small Magellanic Cloud
- Tugela Falls
- a major waterfall in southern Africa; has more than one leap
- tundra
- a vast treeless plain in the Arctic regions where the subsoil is permanently frozen
- Tupungato
- a mountain in the Andes on the border between Argentina and Chile (22,310 feet high)
- turning
- a shaving created when something is produced by turning it on a lathe
- twilight zone
- the lowest level of the ocean to which light can reach
- Twin Falls
- a waterfall in the Snake River in southern Idaho
- twinkler
- an object that emits or reflects light in an intermittent flickering manner
- Tyan Shan
- a major mountain range of central Asia; extends 1,500 miles
- Tyrolean Alps
- a popular tourist area in the Tyrol
- Tyrrhenian Sea
- an arm of the Mediterranean between Italy and the islands of Corsica and Sardinia and Sicily
- Ulugh Muz Tagh
- a mountain in the Kunlun range in China (25,340 feet high)
- Uncompahgre Peak
- the highest peak in the San Juan Mountains of southwestern Colorado (14,309 feet high)
- unit cell
- the smallest group of atoms or molecules whose repetition at regular intervals in three dimensions produces the lattices of a crystal
- United States waters
- territorial waters included within a distance of 12 nautical miles of the coasts of the United States and its territories
- up quark
- a stable quark with an electric charge of +2/3 and a mass 607 times that of an electron
- uphill
- the upward slope of a hill
- Upper Avon River
- a river in central England that flows through Stratford-on-Avon and empties into the Severn
- upper mantle
- the upper part of the mantle
- Upper Peninsula
- the peninsula between Lake Superior and Lake Michigan that forms the northwestern part of Michigan
- Upper Tunguska
- a river in southeastern Siberia that flows northwest from Lake Baikal to become a tributary of the Yenisei River
- Ural Mountains
- a mountain range in western Russia extending from the Arctic to the Caspian Sea; forms part of the traditional boundary between Europe and Asia
- Uranus
- a giant planet with a ring of ice particles; the 7th planet from the sun has a blue-green color and many satellites
- urolith
- a urinary stone
- Ursa Major
- a constellation outside the zodiac that rotates around the North Star
- Urubupunga Falls
- a waterfall in the Parana river in Brazil
- Uruguay River
- a South American river that arises in southern Brazil and flows south to the Rio de la Plata; the northern section forms the boundary between Argentina and Brazil and the southern section forms the boundary between Argentina and Uruguay
- vagabond
- anything that resembles a vagabond in having no fixed place
- vale
- a long depression in the surface of the land that usually contains a river
- valence electron
- an electron in the outer shell of an atom which can combine with other atoms to form molecules
- variable
- something that is likely to vary; something that is subject to variation
- variable
- a star that varies noticeably in brightness
- vector-borne transmission
- indirect transmission of an infectious agent that occurs when a vector bites or touches a person
- Vega
- the brightest star in the constellation Lyra
- vehicle-borne transmission
- indirect transmission of an infectious agent that occurs when a vehicle (or fomite) touches a person's body or is ingested
- Vela
- a constellation in the southern hemisphere between Carina and Pyxis
- vent
- a fissure in the earth's crust (or in the surface of some other planet) through which molten lava and gases erupt
- Venus
- the second nearest planet to the sun; it is peculiar in that its rotation is slow and retrograde (in the opposite sense of the Earth and all other planets except Uranus); it is visible from Earth as an early `morning star' or an `evening star'
- Vesta
- the brightest asteroid but the fourth to be discovered
- vesture
- something that covers or cloaks like a garment
- Vetluga River
- a river in central Russia; flows generally southward into the Volga
- Victoria Falls
- a waterfall in the Zambezi River on the border between Zimbabwe and Zambia; diminishes seasonally
- Victoria Falls
- a large waterfall on the border between Argentina and Brazil
- Victoria Nyanza
- the largest lake in Africa and the 2nd largest fresh water lake in the world; a headwaters reservoir for the Nile River
- viral delivery vector
- a transducing vector that uses a retrovirus
- Virgo
- a large zodiacal constellation on the equator; between Leo and Libra
- virino
- (microbiology) a hypothetical infectious particle thought to be the cause of scrapie and other degenerative diseases of the central nervous system; consists of nucleic acid in a protective coat of host cell proteins
- Vistula River
- a European river; flows into the Baltic Sea
- Volans
- a small constellation in the polar region of the southern hemisphere near Dorado and Carina
- volcano
- a mountain formed by volcanic material
- Volga River
- a Russian river; the longest river in Europe; flows into the Caspian Sea
- Volkhov River
- a river in northwestern Russia flowing generally north into Lake Ladoga
- Volta
- a river in Ghana that flows south to the Bight of Benin
- Vulpecula
- a constellation in the northern hemisphere near Cygnus and Sagitta
- Wabash River
- a tributary of the Ohio River that rises in western Ohio and flows southwestward across Indiana
- wadi
- gully or streambed in northern Africa and the Middle East that remains dry except during rainy season
- wall
- anything that suggests a wall in structure or function or effect
- wall
- a vertical (or almost vertical) smooth rock face (as of a cave or mountain)
- wall rock
- a rock immediately adjacent to a vein or fault
- wallow
- a puddle where animals go to wallow
- water gap
- a pass in a mountain ridge through which a stream flows
- water hole
- a natural hole or hollow containing water
- water system
- a river and all of its tributaries
- watercourse
- natural or artificial channel through which water flows
- waterside
- land bordering a body of water
- waterway
- a navigable body of water
- weakener
- that which weakens or causes a loss of strength
- web
- an intricate network suggesting something that was formed by weaving or interweaving
- webbing
- something forming a web (as between the toes of birds)
- Weddell Sea
- an arm of the south Atlantic in Antarctica to the east of the Antarctic Peninsula
- Weisshorn
- a mountain in the Alps in Switzerland (14,804 feet high)
- Weser River
- a river in northwestern Germany that flows northward to the North Sea near Bremerhaven
- wetland
- a low area where the land is saturated with water
- Wheeler Peak
- a mountain peak in northeastern New Mexico in the Rocky Mountains
- whin
- any of various hard colored rocks (especially rocks consisting of chert or basalt)
- white dwarf
- a faint star of enormous density
- White Nile
- a headstream of the Nile; joins the Blue Nile at Khartoum to form the Nile
- White River
- a tributary of the Mississippi River that flows southeastward through northern Arkansas and southern Missouri
- White Sea
- a large inlet of the Barents Sea in the northwestern part of European Russia
- white water
- frothy water as in rapids or waterfalls
- Wilderness
- a wooded region in northeastern Virginia near Spotsylvania where bloody but inconclusive battles were fought in the American Civil War
- Willamette River
- a river in western Oregon that flows north into the Columbia River near Portland
- WIMP
- a hypothetical subatomic particle of large mass that interacts weakly with ordinary matter through gravitation; postulated as a constituent of the dark matter of the universe
- wind gap
- a pass in a mountain ridge with no stream flowing through it
- window
- an opening that resembles a window in appearance or function
- Windward Passage
- a channel between eastern Cuba and western Haiti that connects the Atlantic Ocean with the Caribbean Sea
- Wisconsin River
- a tributary of the Mississippi River in Wisconsin
- wonderland
- a place or scene of great or strange beauty or wonder
- world
- a part of the earth that can be considered separately
- wormcast
- fossil trail of a worm
- wormhole
- hole made by a burrowing worm
- xenolith
- (geology) a piece of rock of different origin from the igneous rock in which it is embedded
- Yalu River
- river in eastern Asia; rises in North Korea and flows southwest to Korea Bay (forming part of the border between North Korea and China)
- Yangtze Kiang
- the longest river of Asia; flows eastward from Tibet into the East China Sea near Shanghai
- Yazoo River
- a river that rises in west central Mississippi and flows southwest to empty into the Mississippi River above Vicksburg
- Yellow River
- a major river of Asia in northern China; flows generally eastward into the Yellow Sea; carries large quantities of yellow silt to its delta
- Yellow Sea
- part of the Pacific off the east coast of Asia
- Yellowstone River
- a tributary of the Missouri River that flows through the Yellowstone National Park
- Yenisei River
- a Russian river in Siberia; rises in mountains near the Mongolian border and flows generally northward into the Kara Sea
- Yerupaja
- a mountain peak in the Andes in Peru (21,709 feet high)
- Yosemite Falls
- a series of waterfalls in Yosemite National Park in California; is reduced to a trickle for part of each year
- Yukon River
- a North American river that flows westward from the Yukon Territory through central Alaska to the Bering Sea
- Zambezi River
- an African river; flows into the Indian Ocean
- Zuider Zee
- a former inlet of the North Sea in the northern coast of the Netherlands; sealed off from the sea in 1932 by a dam that created the IJsselmeer