In geometry, a skew polygon, saddle polygon, or space polygon, is a polygon whose vertices do not lie in a plane. Skew polygons must have at least 4 vertices. A regular skew polygon is a skew polygon with equal edge lengths and which is vertex-transitive. The interior surface (or area) of such a polygon is not uniquely defined, although this can be considered as a minimal surface problem like the form of a soap film inside of a wire frame.