# Polygon

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Polygons are shapes constructed from a series of straight edges. These edges are defined by a series of vertices.

**Types of Polygons**

**Closed or Open**

A closed polygon shares its first and last vertex and is flagged internally as "closed". Thus, if an open polygon has five vertices, it will still have five vertices when closed. The last (closing) vertex is only implied.

**Planar or Non-planar**

Planar polygons are those whose vertices lie in the same plane in 3D space. Non-planar polygons have vertices that do no lie in the same plane in 3D space.

**Convex or Concave**

A polygon can be convex or concave, as illustrated below:

Convex Polygons

Concave Polygons

A polygon is convex if any vertical or horizontal axis intersects it at most twice.