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 144Â°, therefore making each angle of a regular decagon be 144Â°. Its SchlÃ¤fli symbol is {10}.