A nine-sided polygon is commonly called a nonagon. This polygon, which has nine edges, or vertices, is also called an enneagon. The term enneagon is preferable, but less popular than the name nonagon because the latter is simpler to spell and pronounce, according to Wolfram MathWorld.
The name enneagon is derived from the Greek word ?enneagonon,? which is a combination of two terms that mean nine and corner. The name nonagon, in contrast, has a mixed Roman and Greek origin. It is from the Latin word ?nonus,? which means ninth, added to the suffix ?gonon.? Both enneagon and nonagon are accepted terms to refer to a polygon with nine sides.
Learn MoreA nonagon is a closed shape that has nine sides. If it is a regular nonagon, all nine sides are the same length, and all the angles are equal.
Full Answer >A two-dimensional shape with nine straight sides is called a nonagon. This nine-sided polygon, which also has nine edges or vertices, is also called an enneagon. The term enneagon is preferable, but less popular than the name nonagon because the latter is simpler to spell and pronounce.
Full Answer >An 11-sided polygon is called a hendecagon. In order for an 11-sided shape to be considered a hendecagon, its sides must all be straight and form a closed shape.
Full Answer >A 20-sided polygon is called an icosagon. Along with having 20 sides, all icosagons have 20 interior angles that add up to a total of 3240 degrees.
Full Answer >