A decagonal shape is a polygon with ten sides and ten angles. The term "decagon" comes from the Greek words "deka," meaning ten, and "gonia," meaning angle. Decagons can be regular, where all sides and angles are equal, or irregular, where they vary in length and angle. In geometry, the sum of the interior angles of a decagon is 1,440 degrees. This is calculated using the formula (n-2) × 180, where n is the number of sides. Decagonal shapes can be found in various contexts, including architecture and design, such as in the layout of certain buildings or tiles.