It is called a dodecahedron because it is a polyhedron that has 12 faces (from Greek dodeca- meaning 12).

If you have more than one dodecahedron they are called dodecahedra

Instructions: In "spin" mode it freely spins and will respond to your mouse. In "drag" mode it stops spinning and you can use your mouse to move it. If you cannot see the animation at all, you will need to install "Flash Player".

When we say "dodecahedron" we often mean "regular dodecahedron" (in other words all faces are the same size and shape), but it doesn't have to be - this is also a dodecahedron, even though all faces are not the same.

12-Sided Dice? Yes! A dodecahedron which has 12 equal faces has an equal chance of landing on any face.

In fact, you can make fair dice out of all of the Platonic Solids.