Nonagon
| Regular nonagon (enneagon) | |
|---|---|
 A regular nonagon (enneagon) | |
| Teep | Regular polygon |
| Edges an vertices | 9 |
| Schläfli seembol | {9} |
| Coxeter diagram |    |
| Symmetry group | Dihedral (Dih9), order 2×9 |
| Internal angle (degrees) | 140° |
| Dual polygon | self |
| Properties | convex, cyclic, equilateral, isogonal, isotoxal |
In geometry, a nonagon /ˈnɒnəɡɒn/ (or enneagon /ˈɛniːəɡɒn/) is a nine-sidit regular polygon.
The name "nonagon" is a prefix hybrid formation, frae Laitin (nonus, "ninth" + gonon), uised equivalently, attestit already in the 16t century in French nonogone an in Inglis frae the 17t century. The name "enneagon" comes frae Greek enneagonon (εννεα, "nine" + γωνον (from γωνία = "corner")), an is arguably mair correct, tho somewhit less common nor "nonagon".
A regular nonagon haes internal angles o 140°. The aurie o a regular nonagon o side length a is gien bi
