1. nonagon; enneagon; nine-sided polygon
Wikipedia definition
2. NonagonIn geometry, a nonagon  /ˈnɒnəɡɒn/ is a nine-sided polygon. The name "nonagon" is a prefix hybrid formation, from Latin (nonus, "ninth" + gonon), used equivalently, attested already in the 16th century in French nonogone and in English from the 17th century. The name "enneagon" comes from Greek enneagonon (εννεα, "nine" + γωνον), and is arguably more correct, though somewhat less common. A regular nonagon has internal angles of 140°.
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