009 Mathart - Platonic Solids - Octahedron 03 - 10 cmA Platonic solid is a regular, convex polyhedron. It is constructed by congruent (identical in shape and size) regular (all angles equal and all sides equal) polygonal faces with the same number of faces meeting at each vertex. Five solids meet those criteria: Tetrahedron, Cube, Octahedron, Dodecahedron, Icosahedron.An octahedron is a polyhedron with eight faces, twelve edges, and six vertices.