# Polygon

Pronunciation: /ˈpɒl.iˌgɒn/ Explain

A polygon is an n-sided closed figure in a plane. Each of the sides of a polygon is a straight line segment. Since a polygon is closed, each of the line segments is connected to another at both ends. Examples of polygons are triangles, rectangles, and pentagons. An n-sided polygon is called an n-gon.

### Parts of a polygon

 Illustration 1: Parts of a polygon.

• Each of the line segments that define the polygon is called a side or less commonly, an edge.
• A point where two sides of the polygon meet is called a vertex.
• Everything inside the polygon is called the interior.
• Everything outside the polygon is called the exterior.
• An angle at a vertex on the inside of the polygon is called an interior angle.

### Properties of polygons

• Straight line segments - The edges of polygons are straight line segments. Each line segment is connected to the other line segments at its endpoints.
• closed - Polygons are closed figures. A pencil placed on one point on the edge of the polygon and traced around the edge will return to the same point without retracing.
• Connected - Polygons are all in one piece.
• concave or convex - A polygon can be concave or convex. A polygon is convex if a line segment drawn between any two points in the polygon remains within the polygon.
• Simple or complex - A polygon can be simple or complex. In a simple polygon, none of the edges cross.

### Regular polygon

A regular polygon is a polygon that is simple, convex and equilateral.

### Some Types of polygons

NameSidesIllustration--- Regular ----
Central
angle
Internal
angle
apothem
n-gon n
triangle 3
pentagon 5
hexagon 6
Table 2: Some Types of polygons

### References

1. McAdams, David E.. All Math Words Dictionary, polygon. 2nd Classroom edition 20150108-4799968. pg 141. Life is a Story Problem LLC. January 8, 2015. Buy the book

• McAdams, David E.. Regular Polygon. allmathwords.org. Life is a Story Problem LLC. 3/12/2009. https://www.allmathwords.org/en/r/regularpolygon.html.

McAdams, David E. Polygon. 12/21/2018. All Math Words Encyclopedia. Life is a Story Problem LLC. https://www.allmathwords.org/en/p/polygon.html.

### Revision History

12/21/2018: Reviewed and corrected IPA pronunication. (McAdams, David E.)