Nonagon

In geometry, a nonagon () or enneagon () is a nine-sided polygon or 9-gon.

The name nonagon is a prefixhybrid 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 Greekenneagonon (εννεα, "nine" + γωνον (from γωνία = "corner")), and is arguably more correct, though less common.