# 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.