What are the plationic solids?

Answer 1

Platonic solids are convex regular (equiangular) polyhedra. There are five Platonic solids: the tetrahedron, or pyramid (four equilateral triangles for faces; traditionally associated with the element Fire), the octahedron (eight equilateral triangles; traditionally associated with Air), the icosahedron (twenty equilateral triangles; traditionally associated with Water), the cube (six squares for faces; traditionally associated with Earth), and the dodecahedron (which has twelve regular pentagons for faces and is associated with the legendary Luminiferous Aether that had often been considered an element). These are the only existing regular polyhedra that exhibit convexity; other, non-convex regular polyhedra (meaning that there are angles between some of their faces that are less than 180 degrees as measured from the outside surface) exist and are known as star polyhedra.