What is a 20 sided polyhedron?

20 faceted (regular) polyhedron is a icosahedron - all facets have equal size. There are variations which have more specific names (where certain facets have irregular shapes) An interesting site to look at is polyhedra.org which shows 6 other variations of 20 faceted polyhedrons: 1. gyroelongated triangular cupola

2. parabiaugmented dodecahedron 3. metabiaugmented dodecahedron

4.triangular hebesphenorotunda

5.gyroelongated triangular cupola

6. elongated triangular orthobicupola