A polygon is a closed plane figure formed by line segments.
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.
An irregular polygon has sides or angles that are not congruent, as shown below.
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:
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.