A five-sided shape is called a pentagon. In geometry, all two dimensional shapes are known as polygons, so it can also be referred to as a five-sided polygon.
There are two types of pentagon; regular and irregular. A regular pentagon has five sides of equal length.
An irregular pentagon has five sides of varying length. A regular pentagon will always have the same interior and exterior angles. The interior angle of a regular pentagon is 108 degrees and the exterior angle of a regular pentagon is 72 degrees. The total interior angles of a pentagon will always equal 540 degrees.