Editing Dual polyhedron (section)

===Topological duality===
Even when a pair of polyhedra cannot be obtained by reciprocation from each other, they may be called duals of each other as long as the vertices of one correspond to the faces of the other, and the edges of one correspond to the edges of the other, in an incidence-preserving way. Such pairs of polyhedra are still topologically or abstractly dual.

The vertices and edges of a convex polyhedron form a [[Graph theory|graph]] (the [[n-skeleton|1-skeleton]] of the polyhedron), embedded on the surface of the polyhedron (a topological sphere). This graph can be projected to form a [[Schlegel diagram]] on a flat plane. The graph formed by the vertices and edges of the dual polyhedron is the [[dual graph]] of the original graph.

More generally, for any polyhedron whose faces form a closed surface, the vertices and edges of the polyhedron form a graph embedded on this surface, and the vertices and edges of the (abstract) dual polyhedron form the dual graph of the original graph.

An [[Abstract polytope|abstract polyhedron]] is a certain kind of [[partially ordered set]] (poset) of elements, such that incidences, or connections, between elements of the set correspond to incidences between elements (faces, edges, vertices) of a polyhedron. Every such poset has a dual poset, formed by reversing all of the order relations. If the poset is visualized as a [[Hasse diagram]], the dual poset can be visualized simply by turning the Hasse diagram upside down.

Every geometric polyhedron corresponds to an abstract polyhedron in this way, and has an abstract dual polyhedron. However, for some types of non-convex geometric polyhedra, the dual polyhedra may not be realizable geometrically.