Nouns denoting natural objects (not man-made)

ore bed
a stratum of ore
 
gut
a narrow channel or strait
 
Danube River
the 2nd longest European river (after the Volga); flows from southwestern Germany to the Black Sea
 
Ophiuchus
a large constellation in the equatorial region between Hercules and Scorpius
 
satellite
any celestial body orbiting around a planet or star
 
neutron
an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus
 
existence
everything that exists anywhere
 
divot
(golf) the cavity left when a piece of turf is cut from the ground by the club head in making a stroke
 
cavern
a large cave or a large chamber in a cave
 
Kanawha River
a tributary of the Ohio River in West Virginia
 
terrestrial planet
a planet having a compact rocky surface like the Earth's; the four innermost planets in the solar system
 
Golden Gate
a strait in western California that connects the San Francisco Bay with the Pacific Ocean; discovered in 1579 by Sir Francis Drake
 
Ebro River
a river in northeastern Spain; flows into the Mediterranean
 
Isthmus of Panama
the isthmus that connects Central America and South America; was formerly called the Isthmus of Darien
 
water system
a river and all of its tributaries
 
adjunct
something added to another thing but not an essential part of it
 
Caspian Sea
a large saltwater lake between Iran and Russia fed by the Volga River; the largest inland body of water in the world
 
lake bed
the bottom of a lake
 
oil-water interface
an interface forming the boundary between the non-miscible liquids oil and water
 
eyrie
the lofty nest of a bird of prey (such as a hawk or eagle)
 
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