 Polyhedra with the topological type of a torus are called toroidal polyhedra, and have Euler characteristic "V" − "E" + "F" = 0.For any number of holes, the formula generalizes to "V" − "E" + "F" = 2 − 2"N", where "N" is the number of holes.The term "toroidal polyhedron" is also used for higher-genus polyhedra and for immersions of toroidal polyhedra.