octahedron
A solid figure with twenty faces is called an Icosahedron.
I believe it to be a dodecahedron I believe it to be a dodecahedron +++ You believe correctly: it is a dodecahedron.
A hexahedron is a solid with six plane faces, and a cuboid is a six-sided figure each face of which is a rectangle.
pentahedron
If you ask this, you fail Octahedron
A polyhedron is a solid figure with many plane faces, usually greater than six. A polyhedron that has 7 faces is called a heptahedron.
A decaredra is the ten face solid figure.
A polyhedron with 20 faces is called an icosahedron.
The regular solid, with 20 identical equilateral triangular faces, is called an icosahedron.
It is a regular quadrilateral which is a square
It is called a Nonagon.