**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