Polygon

A polygon is a closed plane figure formed by line segments.

Regular polygons

A regular polygon is a polygon in which all sides have equal length (equilateral) and all angles have equal measure (equiangular). Below are some examples of polygons.

   
Square     Pentagon
 
   
Dodecagon     Triangle

Irregular polygons

An irregular polygon has sides or angles that are not congruent, as shown below.

   
Triangle     6-gon
 
   
8-gon     5-gon

Concave polygons

A concave polygon is a polygon in which one or more of the vertices is "arched inward." A polygon is concave if there is at least one pair of points within the figure that could be joined by a line segment that would go inside the figure:

Convex polygons

A convex polygon is a polygon in which all the vertices are "arched outward." A polygon is convex when each pair of points within the figure could be joined by a line segment that would not go outside the figure:

Did you know?

The word "polygon" is based on Greek words that mean "many" and "angle."


See also plane figure.