# polyhedron

A closed surface consisting of four or more planar *faces*, pairs of which meet at *edges*. The faces form polygons, and the points where three or more edges meet are called *vertices*. The number of faces, edges, and vertices of a polyhedron are related by the Euler polyhedron formula.

A polyhedron with four faces is called a tetrahedron, a pentahedron has five faces, a hexadron six, a heptahedron seven, an octahedron eight, a dodecahedron twelve, and an icosahedron twenty. If all the faces of a polyhedron are congruent, it is called a regular solid or Platonic solid.