Glossary

apex
in a pyramid, the vertex at which all lateral faces meet


base
in a prism, the two congruent, parallel faces at the top and bottom; in a pyramid, the regular polygon that is not a lateral face


congruent
having the same size and shape


cube
a polyhedron with six congruent, square faces


cylinder
a three-dimensional object with circular bases


dodecahedron
a polyhedron with 12 congruent, pentagonal faces


edge
the segment along which two faces meet


Euler's Theorem
for any polyhedron, the sum of the number of vertices and faces is equal to two more than the number of edges; stated another way, F + V - E = 2


face
one of the surfaces of a polyhedron


height
the distance from top to bottom of a three-dimensional figure


icosahedron
a polyhedron with 20 congruent, triangular faces


lateral face
in a prism, one of the rectangles that connects the bases to one another; in a pyramid, one of the triangles that connects the base to the apex


length
the longest dimension of a solid figure; for a three-dimensional figure, it is usually the distance from front to back


octahedron
a polyhedron with eight congruent, triangular faces


polygon
a two-dimensional figure formed by connecting three or more straight line segments end to end (triangles, squares, and hexagons are examples of polygons)


polyhedron
a three-dimensional figure whose faces are polygons


prism
a three-dimensional figure with two parallel, congruent bases connected by rectangles


rectangular prism
a prism whose bases are rectangles; in general, a prism can be described by the shape of its bases


right prism
a prism in which the bases meet the lateral faces at right angles


tetrahedron
a polyhedron with four congruent, triangular faces


truncated icosahedron
a polyhedron with 32 faces, 12 of which are pentagons and 20 of which are hexagons


vertex vertices[plural]
the point at which three or more faces meet


width
distance from side to side