In geometry, a polyhedron (plural polyhedra or polyhedrons) is a geometric solid in three dimensions with flat faces and straight edges. The word polyhedron comes from the Classical Greek πολύεδρον, as poly- (stem of πολύς, "many") + -hedron (form of έδρα, "base", "seat", or "face").
A polyhedron is a 3-dimensional example of the more general polytope in any number of dimensions.
Read more about Polyhedron: Basis For Definition, Names of Polyhedra, Traditional Polyhedra, Generalisations of Polyhedra, Non-geometric Polyhedra, Polyhedra in Nature