Other forms: decahedrons
In geometry, a solid, three-dimensional shape with ten sides is called a decahedron.
In real life, you're most likely to come across a decahedron in the form of a glass or crystal prism. The next time you see one hanging in a window, reflecting rainbows on the wall, count the number of faces, or smooth sides — if there are ten, it's a decahedron. The word comes from Greek roots deka, ten, and hedra, "base" or "face of a geometric solid."