A 12-sided shape is called a dodecagon. A dodecagon is a type of polygon, which is a two-dimensional shape comprised of straight lines. These lines connect to each other to form a closed shape.
The name dodecagon is derived from the Greek words meaning "twelve" (dodeca) and "angles" (gon). Polygons are considered regular polygons if all of their sides and angles are equal. A regular dodecagon has interior angles of 150 degrees. It is also considered a convex dodecagon because none of its interior angles are greater than 180 degrees. Irregular dodecagons have unequal angles and sides. If one of the interior angles is greater than 180 degrees, then it is also a concave dodecagon.