A five-sided polygon, with five vertices and five angles, is called a pentagon. The word pentagon is derived from the Greek words "pente" and "gonia," which mean "five" and "angle."
If a pentagon consists of equal sides and equal angles, it is referred to as a regular pentagon; otherwise, it is called an irregular pentagon. The interior angles of a regular polygon measure 108 degrees. A pentagon consists of five straight, connected sides. If one of the five sides of a given shape is a curved line or if the five-sided shape is not a closed figure, then it is not a pentagon.