**A 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.

The sum of the interior angles of a nonagon is 1260 degrees. If it is a regular nonagon, then all nine angles have the same measurement of 140 degrees.

The term "nonagon" was coined during the 17th century from a combination of words. It begins with the Latin word "nonus," which means "nine." The last part of the word "gon" is patterned after Latin and Greek words meaning "angle. " Literally translated, "nonagon" means "nine angles."