triangle

(geometry) A polygon with three sides and three angles.

(US, Canada) A set square.

(music) A percussion instrument made by forming a metal rod into a triangular shape which is open at one angle. It is suspended from a string and hit with a metal bar to make a resonant sound.

(cue sports) A triangular piece of equipment used for gathering the balls into the formation required by the game being played.

A love triangle.

(systemics) The structure of systems composed with three interrelated objects.

A draughtsman's square in the form of a right-angled triangle.

(historical, usually in the plural) A frame formed of three poles stuck in the ground and united at the top, to which people were bound when undergoing corporal punishment.

Any of various large papilionid butterflies of the genus Graphium.

(rail transport) A triangular formation of railway tracks, with a curve on at least one side.