What is a shape with 11 sides called?

An 11-sided shape is called an undecagon. The term "undecagon" is derived from the Latin word "undecim," meaning eleven, and the Greek word for "angle," "gonia." An undecagon has 11 straight sides and 11 angles.

Since an undecagon has uneven sides and angles, it does not have any special properties like regular polygons (such as equilateral or equiangular polygons). However, it can have various symmetries depending on the placement of its vertices.

The sum of the interior angles in any undecagon is given by the formula: (n-2) * 180°, where n is the number of sides. Applying this formula, the sum of the interior angles of an undecagon would be (11-2) * 180° = 1620°.

Undecagons are not commonly found in nature or extensively used in architecture. However, they can be utilized in various mathematical and geometric designs, optical illusions, and tessellations.

It is important to note that the term "hendecagon" is also used to describe an 11-sided polygon, although "undecagon" is more commonly used.