In geometry, a decahedron is a polyhedron with ten faces. There are 32300 topologically distinct decahedra and none is regular, so this name is ambiguous.With regular faces:Octagonal prism (uniform 8-prism)Square antiprism (uniform 4-antiprism)Square cupola (Johnson solid 4)Pentagonal dipyramid (Johnson solid 13, 5-bipyramid)Augmented pentagonal prism (Johnson solid 52)With irregular faces it can also be:Pentagonal trapezohedron (5-trapezohedron, antiprism dual) — often used as a die in role playing games, known as d10Enneagonal pyramid (9-pyramid)