Icosahedron
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In geometry, an icosahedron is a polyhedron with 20 faces. The name comes from Ancient Greek εἴκοσι (eíkosi) 'twenty', and ἕδρα (hédra) 'seat'. The plural can be either "icosahedra" or "icosahedrons".
Three interlocking golden rectangles inscribed in a convex regular icosahedron
A detail of Spinoza monument in Amsterdam
Polyhedron
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In geometry, a polyhedron is a three-dimensional shape with flat polygonal faces, straight edges and sharp corners or vertices.
Convex polyhedron blocks on display at the Universum museum in Mexico City
Problem 14 of the Moscow Mathematical Papyrus, on calculating the volume of a frustum
14-sided die from the Warring States period
Doppio ritratto, attributed to Jacopo de' Barbari, depicting Luca Pacioli and a student studying a glass rhombicuboctahedron half-filled with water.