In geometry, a nonagon (/ ˈ n ɒ n ə ɡ ɒ n /) or enneagon (/ ˈ ɛ n i ə ɡ ɒ n /) is a nine-sided polygon or 9-gon. 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. read more