Face (geometry)

In solid geometry, a face is a flat surface (a planar region) that forms part of the boundary of a solid object;^[1] a three-dimensional solid bounded exclusively by faces is a polyhedron.

In more technical treatments of the geometry of polyhedra and higher-dimensional polytopes, the term is also used to mean an element of any dimension of a more general polytope (in any number of dimensions).^[2]