A dodecahedron has 30 edges that are shared by 12 faces. A regular dodecahedron is a three-dimensional shape where all the faces are pentagons.
There are many different types of dodecahedron, such as the rhombic or pyritohedral dodecahedron. Both of these variations lack regular pentagonal faces, which means that all of their edge lengths are not the same. Different types of dodecahedrons have different numbers of edges.
A regular dodecahedron is a highly symmetrical shape, having multiple lines of symmetry. There are other 12-sided shapes that have limited or no symmetry, usually consisting of a mixture of pentagonal, square or triangular faces.