- tetrahedron: 4 sides.
- cube: 6 sides.
- octahedron: 8 sides.
- dodecahedron: 12 sides.
- icosahedron: 20 sides.

Caption: The 5---and there are only 5---Platonic solids (i.e., regular, convex polyhedrons):

The 5 Platonic solids may have been what Plato (428/427--348/347 BCE) had in mind when discussing Platonic ideals---the true things of which all things observable are imperfect manifestations of.

But can there be a Platonic ideal horse? Pegasus?

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