**A pentagon is a two-dimensional geometric figure that has five sides.** A regular pentagon is one where all five sides are the exact same length and the internal angles are all 108 degrees.

In addition to having five sides, the sides must also form a closed shape. Sides also must be straight. Pentagons can be regular or irregular. An irregular pentagon refers to any pentagon where all sides are not equal, which consequently means that their angles are not equal, either. Other closely related shapes to pentagons include four-sided shapes, quadrilaterals, and six-sided shapes, which are called hexagons.