icosahedron
A six faced 3d shape is called a cube.
Oh, dude, a 20-faced 3D shape is technically called an icosahedron. It's like a fancy way of saying it's a shape with 20 sides or faces. So, next time you see a 20-faced shape, just casually drop the term "icosahedron" and watch everyone be like, "Whoa, this person knows their geometry!"
Enneahedral
A hendecahedron.
A twelve sided shape is called a "dodecahedron" :D
A pyramid.
Decahedreon
It is a nonahedron.
An 8-faced 3D shape is called an octahedron. It is a polyhedron with eight triangular faces, 12 edges, and six vertices.
It is called a trihedron. It does not exist.
Dodecahedron.