1. A plain figure having nine angles.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• bonagon,
• monagon,
• jonagon,
• honagon,
• ninagon,
• nknagon,
• nlnagon,
• npnagon,
• n0nagon,
• n9nagon,
• nobagon,
• nomagon,
• nojagon,
• nongon,
• nonogon,
• nannagon,
• nineagon,
• nonegeon,
• nonagen,
• noneagon

The adjective form of the word "nonagon" is "nonagonal".

The plural of the "nonagon" can be the "nonagons".

The singular of the "nonagon" can be the "nonagon".