dodecahedron
There is no name for a five sided regular polygon. A five sided polyhedron is called a pentahedron.
icosahedron (its a 20 sided trinagular faced polyhedron)
A polyhedron with 20 faces is called an icosahedron.
A six sided polyhedron is a hexahedron. This may be a triangle based dipyramid, a pentagonal pyramid of a variant of a parallelepiped.
A 120-sided polyhedron is a hecatonicosahedron.
dodecahedron
There is no name for a five sided regular polygon. A five sided polyhedron is called a pentahedron.
icosahedron (its a 20 sided trinagular faced polyhedron)
A polyhedron with 20 faces is called an icosahedron.
A six sided polyhedron is a hexahedron. This may be a triangle based dipyramid, a pentagonal pyramid of a variant of a parallelepiped.
A 20-sided polyhedron is called an icosahedron. It has 20 equilateral triangle faces, 30 edges, and 12 vertices. It is a regular convex polyhedron with rotational symmetry.
nonahedron
A many sided planar figure is a polygon. A many sided solid is a polyhedron.
A 20-sided polyhedron is an icosahedron. A 20-sided polygon is an icosagon.
An octahedron, which looks like 2 pyramids glued bottom to bottom.
an icosahedron (icosagon) is a regular polyhedron with 20 identical equilateral triangular faces