Decagon :: Decagon (n.) A plane figure having ten sides and ten angles; any figure having ten angles. A regular decagon is one that has all its sides and angles equal.
Decagonal :: Decagonal (a.) Pertaining to a decagon; having ten sides.
Dodecagon :: Dodecagon (n.) A figure or polygon bounded by twelve sides and containing twelve angles.
Endecagon :: Endecagon (n.) A plane figure of eleven sides and angles.
Hendecagon :: Hendecagon (n.) A plane figure of eleven sides and eleven angles.
Quindecagon :: Quindecagon (n.) A plane figure with fifteen angles, and consequently fifteen sides..
Undecagon :: Undecagon (n.) A figure having eleven angles and eleven sides.