In geometry, a dodecahedron (Greek δωδεκάεδρον, from δώδεκα, dōdeka "twelve" + ἕδρα hédra "base", "seat" or "face") is any polyhedron with twelve flat faces, but usually a regular dodecahedron is meant: a Platonic solid. It is composed of 12 regular pentagonal faces, with three meeting at each vertex, and is represented by the Schläfli symbol {5,3}. It has 20 vertices, 30 edges and 160 diagonals. Its dual polyhedron is the icosahedron, with Schläfli symbol {3,5}. A large number of other (irregular) polyhedra also have twelve faces, most notably the topologically identical pyritohedron with Pyritohedral symmetry, and the rhombic dodecahedron with octahedral symmetry. [Dodecahedron. Wikipedia]