A polygon/shape that has ten angles and ten straight lines.
a polygon with 10 sides and 10 angles
A plane figure with ten sides and ten angles.
A decagon is a ten-sided geometric figure.
A decagon is a ten-sided shape (polygon).
A ten-sided polygon (Lesson 2.5).
In geometry, a decagon is any polygon with ten sides and ten angles, and usually refers to a regular decagon, having all sides of equal length and all angles equal to 144°, therefore making each angle of a regular decagon be 144°. Its Schläfli symbol is {10}.