Simple Polygon

A Polygon $P$ is said to be simple (or Jordan) if the only points of the plane belonging to two Edges of $P$ are the Vertices of $P$. Such a polygon has a well-defined interior and exterior.

See also Polygon, Regular Polygon, Two-Ears Theorem

References

Toussaint, G. ``Anthropomorphic Polygons.'' Amer. Math. Monthly 122, 31-35, 1991.