What Is a Nine-Sided Shape Called?

By Staff WriterLast Updated Mar 27, 2020 4:19:39 AM ET
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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.

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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."