A fifteen-sided shape is known as a pentadecagon. This polygon has fifteen straight edges and fifteen vertices. The term "pentadecagon" comes from the Greek words "penta," meaning five, and "deca," meaning ten, indicating its total of fifteen sides. In geometry, the interior angles of a pentadecagon can be calculated using the formula (n-2) \times 180 degrees, where n is the number of sides. For a pentadecagon, the sum of the interior angles is 2340 degrees, making each interior angle approximately 156 degrees when the shape is regular, meaning all sides and angles are equal.