# Nouns denoting two and three dimensional shapes

acantha
any sharply pointed projection

acute angle
an angle less than 90 degrees but more than 0 degrees

acute triangle
a triangle whose interior angles are all acute

altitude
the perpendicular distance from the base of a geometric figure to the opposite vertex (or side if parallel)

amorphous shape
an ill-defined or arbitrary shape

anchor ring
a toroidal shape

angle
the space between two lines or planes that intersect; the inclination of one line to another; measured in degrees or radians

angle of attack
the acute angle between the direction of the undisturbed relative wind and the chord of an airfoil

angle of dip
(physics) the angle that a magnetic needle makes with the plane of the horizon

angle of extinction
the angle from its axis that a crystal must be rotated before appearing maximally dark when viewed in polarized light

angle of incidence
the angle that a line makes with a line perpendicular to the surface at the point of incidence

angle of inclination
(geometry) the angle formed by the x-axis and a given line (measured counterclockwise from the positive half of the x-axis)

angle of reflection
the angle between a reflected ray and a line perpendicular to the reflecting surface at the point of incidence

angle of refraction
the angle between a refracted ray and a line perpendicular to the surface between the two media at the point of refraction

angle of view
the angle included by a photographic lens

angular distance
the angular separation between two objects as perceived by an observer

angular shape
a shape having one or more sharp angles

arc
a continuous portion of a circle

arc
something curved in shape

arch
a curved shape in the vertical plane that spans an opening

articulation
the shape or manner in which things come together and a connection is made

asterism
(mineralogy) a star-shaped figure with six rays that is seen in some crystal structures under reflected or transmitted light

asymptote
a straight line that is the limiting value of a curve; can be considered as tangent at infinity

AZ
the azimuth of a celestial body is the angle between the vertical plane containing it and the plane of the meridian

balance
equality of distribution

ball
an object with a spherical shape

barrel
a bulging cylindrical shape; hollow with flat ends

base
the bottom side of a geometric figure from which the altitude can be constructed

a shape that is spherical and small

bell
the shape of a bell

belly
a part that bulges deeply

bend
an angular or rounded shape made by folding

bend
a circular segment of a curve

bias
a line or cut across a fabric that is not at right angles to a side of the fabric

bifurcation
the place where something divides into two branches

bifurcation
a bifurcating branch (one or both of them)

bight
a bend or curve (especially in a coastline)

bight
a loop in a rope

blob
an indistinct shapeless form

block
a three-dimensional shape with six square or rectangular sides

bolus
a small round soft mass (as of chewed food)

border
the boundary line or the area immediately inside the boundary

bottleneck
a narrowing that reduces the flow through a channel

bound
a line determining the limits of an area

bowl
a concave shape with an open top

box
a rectangular drawing

brachium
(biology) a branching or armlike part of an animal

branch
a part of a forked or branching shape

brink
a region marking a boundary

buckle
a shape distorted by twisting or folding

bulb
anything with a round shape resembling a teardrop

bulge
something that bulges out or is protuberant or projects from its surroundings

camber
a slight convexity (as of the surface of a road)

caput
a headlike protuberance on an organ or structure

cardioid
an epicycloid in which the rolling circle equals the fixed circle

Cartesian plane
a plane in which all points can be described in Cartesian coordinates

cast
the distinctive form in which a thing is made

catenary
the curve theoretically assumed by a perfectly flexible and inextensible cord of uniform density and cross section hanging freely from two fixed points

cavity
space that is surrounded by something

center line
a line that bisects a plane figure

channel
a long narrow furrow cut either by a natural process (such as erosion) or by a tool (as e.g. a groove in a phonograph record)

chap
a long narrow depression in a surface

chord
a straight line connecting two points on a curve

circle
something approximating the shape of a circle

circle
ellipse in which the two axes are of equal length; a plane curve generated by one point moving at a constant distance from a fixed point

circlet
a small circle

a tree diagram used to illustrate phylogenetic relationships

cleft
a split or indentation in something (as the palate or chin)

closed curve
a curve (such as a circle) having no endpoints

coil
a round shape formed by a series of concentric circles (as formed by leaves or flower petals)

columella
a small column (or structure resembling a column) that is a part of a plant or animal

column
anything that approximates the shape of a column or tower

complementary angles
two angles whose sum is a right angle

complex plane
a geometric representation of the complex numbers established by the real axis and the orthogonal imaginary axis; it can be thought of as a modified Cartesian plane, with the real part of a complex number represented by a displacement along the x-axis, and the imaginary part by a displacement along the y-axis

concave polygon
a polygon such that there is a straight line that cuts it in four or more points

concave polyhedron
a polyhedron some of whose plane sections are concave polygons

concave shape
a shape that curves or bends inward

cone
a shape whose base is a circle and whose sides taper up to a point

conformation
a symmetrical arrangement of the parts of a thing

conglobation
a rounded spherical form

conic
(geometry) a curve generated by the intersection of a plane and a circular cone

connection
a connecting shape

contortion
a tortuous and twisted shape or position

convex polygon
a polygon such that no side extended cuts any other side or vertex; it can be cut by a straight line in at most two points

convex polyhedron
a polyhedron any plane section of which is a convex polygon

convex shape
a shape that curves or bulges outward

convolution
the shape of something rotating rapidly

corner
a small concavity

corrugation
a ridge on a corrugated surface

crease
a slight depression or fold in the smoothness of a surface

crenation
one of a series of rounded projections (or the notches between them) formed by curves along an edge (as the edge of a leaf or piece of cloth or the margin of a shell or a shriveled red blood cell observed in a hypertonic solution etc.)

crescent
any shape resembling the curved shape of the moon in its first or last quarters

critical angle
the smallest angle of incidence for which light is totally reflected

crotch
the region of the angle formed by the junction of two branches

crotchet
a sharp curve or crook; a shape resembling a hook

crow's feet
a wrinkle in the skin at the outer corner of your eyes

cube
a hexahedron with six equal squares as faces

cuboid
a rectangular parallelepiped

cuneus
any shape that is triangular in cross section

cup
any cup-shaped concavity

Cupid's bow
the double curve of the upper lip when considered to resemble Cupid's bow

curtate cycloid
a cycloid generated by a point inside the rolling circle

curve
the trace of a point whose direction of motion changes

cutting angle
the angle between the face of a cutting tool and the surface of the work

cycloid
a line generated by a point on a circle rolling along a straight line

cylinder
a surface generated by rotating a parallel line around a fixed line

cylinder
a solid bounded by a cylindrical surface and two parallel planes (the bases)

decagon
a polygon with 10 sides and 10 angles

decahedron
any polyhedron having ten plane faces

delta
an object shaped like an equilateral triangle

dent
a depression scratched or carved into a surface

depression
a concavity in a surface produced by pressing

dermatoglyphic
the lines that form patterns on the skin (especially on the fingertips and the palms of the hands and the soles of the feet)

dewdrop
a drop of dew

diagonal
(geometry) a straight line connecting any two vertices of a polygon that are not adjacent

diameter
a straight line connecting the center of a circle with two points on its perimeter (or the center of a sphere with two points on its surface)

diamond
a parallelogram with four equal sides; an oblique-angled equilateral parallelogram

dimple
any slight depression in a surface

dip
a depression in an otherwise level surface

disc
something with a round shape resembling a flat circular plate

disproportion
lack of proportion; imbalance among the parts of something

distorted shape
a shape resulting from distortion

dodecagon
a twelve-sided polygon

dodecahedron
any polyhedron having twelve plane faces

dogleg
angle that resembles the hind leg of a dog

dome
a concave shape whose distinguishing characteristic is that the concavity faces downward

dot
a very small circular shape

double helix
a pair of parallel helices intertwined about a common axis

droop
a shape that sags

eccentricity
(geometry) a ratio describing the shape of a conic section; the ratio of the distance between the foci to the length of the major axis

element
a straight line that generates a cylinder or cone

element of a cone
a straight line joining the apex and a point on the base

element of a cylinder
a straight line running the length of the cylinder

ellipse
a closed plane curve resulting from the intersection of a circular cone and a plane cutting completely through it

ellipsoid
a surface whose plane sections are all ellipses or circles

ellipsoid of revolution
a shape that is generated by rotating an ellipse around one of its axes

emptiness
an empty area or space

entasis
a slight convexity in the shaft of a column; compensates for the illusion of concavity that viewers experience when the sides are perfectly straight

envelope
a curve that is tangent to each of a family of curves

epicycle
a circle that rolls around (inside or outside) another circle; generates an epicycloid or hypocycloid

epicycloid
a line generated by a point on a circle rolling around another circle

equator
a circle dividing a sphere or other surface into two usually equal and symmetrical parts

equiangular triangle
a three-sided regular polygon

equilateral
a figure whose sides are all equal

exterior angle
the supplement of an interior angle of a polygon

the exterior curve of an arch

face angle
the angle formed by two edges of a polyhedral angle

facet
a smooth surface (as of a bone or cut gemstone)

facet plane
the plane of a facet of an object (as of a cube)

figure
a combination of points and lines and planes that form a visible palpable shape

figure 8
a two-dimensionsal figure having the shape of the number eight

flair

flank
a subfigure consisting of a side of something

forking
the place where something divides into branches

fossa
a concavity in a surface (especially an anatomical depression)

foursquare
(geometry) a plane rectangle with four equal sides and four right angles; a four-sided regular polygon

fringe
the outside boundary or surface of something

frown line
a facial wrinkle associated with frowning

frustum
a truncated cone or pyramid; the part that is left when a cone or pyramid is cut by a plane parallel to the base and the apical part is removed

funnel
a conical shape with a wider and a narrower opening at the two ends

geodesic
(mathematics) the shortest line between two points on a mathematically defined surface (as a straight line on a plane or an arc of a great circle on a sphere)

gnarl
something twisted and tight and swollen

gooseneck
something in a thin curved form (like the neck of a goose)

HA
(astronomy) the angular distance of a celestial point measured westward along the celestial equator from the zenith crossing; the right ascension for an observer at a particular location and time of day

heart
a plane figure with rounded sides curving inward at the top and intersecting at the bottom; conventionally used on playing cards and valentines

heart line
a crease on the palm; palmists say it indicates your emotional nature

helix angle
the constant angle at which a helix cuts the elements of a cylinder or cone

helix
a curve that lies on the surface of a cylinder or cone and cuts the element at a constant angle

hemicycle
a plane figure with the shape of half a circle

hemisphere
half of a sphere

heptagon
a seven-sided polygon

hexagon
a six-sided polygon

hexagram
a regular polygon formed by extending each of the sides of a regular hexagon to form two equilateral triangles

hexahedron
any polyhedron having six plane faces

hip
(architecture) the exterior angle formed by the junction of a sloping side and a sloping end of a roof

hole
an unoccupied space

hollow
a cavity or space in something

hoodoo
(geology) a column of weathered and unusually shaped rock

hyperbola
an open curve formed by a plane that cuts the base of a right circular cone

hyperboloid
a quadric surface generated by rotating a hyperbola around its main axis

hypocycloid
a line generated by a point on a circle that rolls around inside another circle

hypotenuse
the side of a right triangle opposite the right angle

icosahedron
any polyhedron having twenty plane faces

incisura
(anatomy) a notch or small hollow

inclination
(astronomy) the angle between the plane of the orbit and the plane of the ecliptic stated in degrees

indentation
a concave cut into a surface or edge (as in a coastline)

interior angle
the angle inside two adjacent sides of a polygon

intersection
a point or set of points common to two or more geometric configurations

the interior curve of an arch

isogon
an equiangular polygon

isosceles triangle
a triangle with two equal sides

jog
a sharp change in direction

Jordan curve
a closed curve that does not intersect itself

keel
a projection or ridge that suggests a keel

kink
a sharp bend in a line produced when a line having a loop is pulled tight

knife
any long thin projection that is transient

knob
any thickened enlargement

the angle between the direction a gun is aimed and the position of a moving target (correcting for the flight time of the missile)

leaf form
any of the various shape that leaves of plants can assume

lemniscate
any of several plane algebraic curves in the shape of a figure eight

life line
a crease on the palm; its length is said by palmists to indicate how long you will live

line
a length (straight or curved) without breadth or thickness; the trace of a moving point

line of Saturn
a crease on the palm; palmists say it indicates how successful you will be

line roulette
a line generated by a point on one figure rolling around a second figure

loop
anything with a round or oval shape (formed by a curve that is closed and does not intersect itself)

lower bound
(mathematics) a number equal to or less than any other number in a given set

magnetic declination
the angle (at a particular location) between magnetic north and true north

midline
the median plane of the body (or some part of the body)

mogul
a bump on a ski slope

natural shape
a shape created by natural forces; not man-made

node
a connecting point at which several lines come together

nonagon
a nine-sided polygon

notch
a V-shaped indentation

nub
a small lump or protuberance

oblique angle
an angle that is not a right angle or a multiple of a right angle

oblique triangle
a triangle that contains no right angle

oblong
a plane figure that deviates from a square or circle due to elongation

obtuse angle
an angle between 90 and 180 degrees

obtuse triangle
a triangle that contains an obtuse interior angle

octagon
an eight-sided polygon

octahedron
any polyhedron having eight plane faces

orbital plane
(astronomy) the plane on which a body is orbiting

ovoid
an egg-shaped object

parabola
a plane curve formed by the intersection of a right circular cone and a plane parallel to an element of the curve

paraboloid
a surface having parabolic sections parallel to a single coordinate axis and elliptic sections perpendicular to that axis

parallel
(mathematics) one of a set of parallel geometric figures (parallel lines or planes)

parallelepiped
a prism whose bases are parallelograms

parallelogram
a quadrilateral whose opposite sides are both parallel and equal in length

peak
a V shape

pellet
a small sphere

pencil
a figure formed by a set of straight lines or light rays meeting at a point

pentacle
a star with 5 points; formed by 5 straight lines between the vertices of a pentagon and enclosing another pentagon

pentagon
a five-sided polygon

pentahedron
any polyhedron having five plane faces

perigon
an angle of 360 degrees

perimeter
a line enclosing a plane areas

perpendicular
a straight line at right angles to another line

perversion
a curve that reverses the direction of something

picture plane
the plane that is in the foreground of a drawing or painting; coextensive with but different from the objective surface of the work

pipe
a hollow cylindrical shape

plane angle
an angle formed by two straight lines (in the same plane)

plane figure
a two-dimensional shape

plane
(mathematics) an unbounded two-dimensional shape

Platonic solid
any one of five solids whose faces are congruent regular polygons and whose polyhedral angles are all congruent

plume
anything that resembles a feather in shape or lightness

pocket
(bowling) the space between the headpin and the pins behind it on the right or left

pocket
an enclosed space

pocket
a hollow concave shape made by removing something

polygon
a closed plane figure bounded by straight sides

polyhedral angle
the space enclosed by three or more planes that intersect in a vertex

polyhedron
a solid figure bounded by plane polygons or faces

pore
any tiny hole admitting passage of a liquid (fluid or gas)

prism
a polyhedron with two congruent and parallel faces (the bases) and whose lateral faces are parallelograms

prismatoid
a polyhedron whose vertices all lie in one or the other of two parallel planes; the faces that lie in those planes are the bases of the prismatoid

prismoid
a prismatoid whose bases are polygons having the same number of sides and whose other faces are trapezoids or parallelograms

projection
any solid convex shape that juts out from something

prolate cycloid
a cycloid generated by a point outside the rolling circle

proportion
balance among the parts of something

pucker
an irregular fold in an otherwise even surface (as in cloth)

pyramid
a polyhedron having a polygonal base and triangular sides with a common vertex

a four-sided polygon

a prism whose bases are quadrangles

a square-shaped object

a cubelike object

a curve or surface whose equation (in Cartesian coordinates) is of the second degree

a straight line from the center to the perimeter of a circle (or from the center to the surface of a sphere)

ray
(mathematics) a straight line extending from a point

rectangle
a parallelogram with four right angles

reentering angle
an interior angle of a polygon that is greater than 180 degrees

reentering polygon
a polygon with one or more reentrant angles

reflex angle
an angle greater than 180 degrees (but less than 360)

regular dodecahedron
a dodecahedron with twelve regular pentagons as faces

regular hexagon
a hexagon with six sides of equal length

regular icosahedron
an icosahedron with twenty equilateral triangles as faces

regular octahedron
an octahedron with eight equilateral triangles as faces

regular polygon
a polygon with all sides and all angles equal

regular tetrahedron
a tetrahedron with four equilateral triangular faces

rhombohedron
a parallelepiped bounded by six similar faces (either rhombuses or parallelograms)

rhomboid
a parallelogram with adjacent sides of unequal lengths; an oblique-angled parallelogram with only the opposite sides equal

ridge
any long raised strip

right angle
the 90 degree angle between two perpendicular lines

right triangle
a triangle with one right angle

rim
the shape of a raised edge of a more or less circular object

round shape
a shape that is curved and without sharp angles

rut
a groove or furrow (especially one in soft earth caused by wheels)

S-shape
a double curve resembling the letter S

salient angle
an angle pointing outward; an interior angle of a polygon that is less than 180 degrees

scalene triangle
a triangle with no two sides of equal length

score
a slight surface cut (especially a notch that is made to keep a tally)

secant
a straight line that intersects a curve at two or more points

sector
a plane figure bounded by two radii and the included arc of a circle

shapelessness
an amorphous or indefinite shape

sine curve
the curve of y=sin x

sinuosity
having curves

snag
a sharp protuberance

solid
a three-dimensional shape

solid angle
an angle formed by three or more planes intersecting at a common point (the vertex)

solid figure
a three-dimensional shape

space
an empty area (usually bounded in some way between things)

sphere
a three-dimensional closed surface such that every point on the surface is equidistant from the center

sphere
a solid figure bounded by a spherical surface (including the space it encloses)

spherical angle
an angle formed at the intersection of the arcs of two great circles

spherical polygon
a figure on the surface of a sphere bounded by arcs of 3 or more great circles

spherical triangle
a spherical polygon formed by the arcs of 3 great circles

spherule
a small sphere

spiral
a plane curve traced by a point circling about the center but at increasing distances from the center

square
something approximating the shape of a square

star
a plane figure with 5 or more points; often used as an emblem

stemma
a tree diagram showing a reconstruction of the transmission of manuscripts of a literary work

straight line
a line traced by a point traveling in a constant direction; a line of zero curvature

stria
any of a number of tiny parallel grooves such as: the scratches left by a glacier on rocks or the streaks or ridges in muscle tissue

subfigure
a figure that is a part of another figure

tail
any projection that resembles the tail of an animal

tangent
a straight line or plane that touches a curve or curved surface at a point but does not intersect it at that point

tangent plane
the plane that contains all the lines tangent to a specific point on a surface

taper
a convex shape that narrows toward a point

teardrop
anything shaped like a falling drop (as a pendant gem on an earring)

tesseract
the four-dimensional analogue of a cube

tetrahedron
any polyhedron having four plane faces

thalweg
the middle of the chief navigable channel of a waterway that forms the boundary line between states

tilt angle
the angle a rocket makes with the vertical as it curves along its trajectory

toroid
the doughnut-shaped object enclosed by a torus

toroid
a ring-shaped surface generated by rotating a circle around an axis that does not intersect the circle

trapezium
a quadrilateral with no parallel sides

trapezohedron
a polyhedron whose faces are trapeziums

trapezoid
a quadrilateral with two parallel sides

tree
a figure that branches from a single root

triangle
something approximating the shape of a triangle

triangle
a three-sided polygon

triangular prism
a prism whose bases are triangles

true anomaly
the angular distance of a point in an orbit past the point of periapsis measured in degrees

truncated cone
a frustum formed from a cone

truncated pyramid
a frustum formed from a pyramid

uncus
(biology) any hook-shaped process or part

undecagon
an eleven-sided polygon

undulation
an undulating curve

upper bound
(mathematics) a number equal to or greater than any other number in a given set

vector
a straight line segment whose length is magnitude and whose orientation in space is direction

vertical angle
either of two equal and opposite angles formed by the intersection of two straight lines

verticil
a whorl of leaves growing around a stem

wart
any small rounded protuberance (as on certain plants or animals)

washout
the channel or break produced by erosion of relatively soft soil by water

wave angle
the angle of arrival (or departure) of a radio wave with respect to the axis of an antenna array

zag
an angular shape characterized by sharp turns in alternating directions