Polyhedron

A polyhedron (plural polyhedra) is a solid whose faces are all plane polygons. The faces need not be regular polygons. (A regular polygon is a polygon whose edges are all congruent and whose angles are all equal) If the faces of a polyhedron are all identical regular polygons then the polyhedron is referred to as a regular polyhedron, or a Platonic solid.

If the faces of a polyhedron are all regular polygons but are not identical, then the polyhedron is referred to as a semi-regular polyhedron, or an Archimedean solid.