The term for a polygon with eight sides is "octagon." Octagons are two-dimensional geometric shapes characterized by their eight straight edges and eight vertices. Regular octagons have all sides and angles equal, while irregular octagons can have sides and angles of different lengths and measures. An example of a regular octagon is a stop sign, which is customary in many countries and is easily recognized for its distinctive shape. In mathematics, octagons can be studied in geometry, and their properties are relevant in various applications, including architecture and design.