What is a 20-sided shape called?

A 20-sided shape is known as an icosagon. The icosagon is a polygon, and the sum of its interior angles is equivalent to 3,240 degrees.

Notably, when contestants spin the "Big Wheel" on the popular long-running TV game show "The Price Is Right," they are spinning an icosagon-shaped wheel. In addition, the outdoor theater where William Shakespeare and his acting company performed, the Globe, was built on an icosagon-shaped foundation.

Polygons with three to 20 sides are named with a Greek prefix and the "gon" suffix. For example, an eight-sided polygon is called an octagon, formed from the Greek "octa" and the suffix "gon."