Triskaidecagonal

Triskaidecagonal refers to a polygon with thirteen sides. The word itself is derived from the Greek word "treiskaideka" meaning thirteen, and "gonia" meaning angle or corner. A triskaidecagon is therefore a thirteen-sided polygon. Like any polygon, it is a closed two-dimensional shape made up of straight line segments.

A regular triskaidecagon has thirteen equal sides and thirteen equal interior angles. The measure of each interior angle in a regular triskaidecagon can be calculated using the formula (n-2) * 180 / n, where n is the number of sides. For a triskaidecagon, this equates to (13-2) * 180 / 13, which is approximately 152.31 degrees. The sum of the interior angles of any triskaidecagon, regular or irregular, is always (13-2) * 180 degrees, or 1980 degrees.

While less commonly encountered in everyday geometry than shapes like triangles or squares, triskaidecagons do appear in various contexts, including in some architectural designs or decorative patterns where the number thirteen is intentionally incorporated. The concept of a thirteen-sided polygon is a straightforward extension of the definition of polygons.