
1.  A solid that is bounded by polygons, called faces, that enclose a single region of space. 
2.  A cone with a vertex that lies directly above the center of the base. 
5.  A plane figure that meets the following two conditions. (1) It is formed by three or more segments called sides, such that no two sides with a common endpoint are collinear. (2) Each side intersects exactly two other sides, one at each endpoint. 
7.  A cylinder such that the segment joining the centers of the bases is perpendicular to the bases. 
8.  A prism whose lateral edges are not perpendicular to the bases. 
11.  A line segment formed by the intersection of two faces of a polyhedron. 
12.  The ratio of the lengths of two corresponding sides of two similar polygons. 


1.  Five regular polyhedra, named after the Greek mathematician and philosopher Plato, including a regular tetrahedron, a cube, a regular octahedron, a regular dodecahedron, and a regular icosahedron. 
2.  A prism whose lateral edges are perpendicular to both bases. 
3.  A solid with congruent circular bases that lie in parallel planes. 
4.  Half of a sphere, formed when a great circle separates a sphere into two congruent halves. 
6.  A polyhedron with two congruent faces, called bases, that lie in parallel planes. 
9.  The locus of points in space that are a given distance from a point, called the center. 
10.  A twodimensional representation of all the faces of a polyhedron. 