A pentagon is a five-sided polygon, which is a flat shape with straight edges. Each of the five angles in a regular pentagon measures 108 degrees, and the sum of all interior angles is 540 degrees. Pentagons can be found in various forms, including regular pentagons, where all sides and angles are equal, and irregular pentagons, which have sides and angles of different lengths and measures. Pentagons are commonly seen in architecture and design, such as in the structure of the Pentagon building in Arlington, Virginia. They also appear in nature and art, making them an interesting subject in geometry and mathematics.