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 (nonregular) polyhedra also have 12 sides, but are given other names. Other dodecahedra include the hexagonal bipyramid and the rhombic dodecahedron.

Read more about Dodecahedron: Dimensions, Area and Volume, Two Dimensional Symmetry Projections, Cartesian Coordinates, Properties, Geometric Relations, Related Polyhedra, Other Dodecahedra, History and Uses, As A Graph