A polygon is a closed plane figure containing three or more angles and bounded by three or more straight sides. The word polygon itself means “many corners”.

The following figures are all polygons:

- A three-sided polygon is called triangle
- Rectangle and square are examples of four-sided polygons
- A pentagon is a five-sided polygon

A regular polygon is one in which all sides are the same length and all angles are equal.

A square is an example of regular polygon.

The perimeter of any polygon is simply the distance around the outside of the polygon.