triangle Definition

triangle
noun

1. geom.
A two-dimensional figure that has three sides and three internal angles which always total 180°.
2. Anything of a similar shape.
3. A simple musical percussion instrument made from a metal bar which has been bent into a trianglular shape with one corner left open and which is played by striking it with a small metal hammer.
4. An emotional relationship or love affair that involves three people.

Example: involved in an eternal triangle
5. A fluorescent triangular sign that is placed at the roadside to warn other road users of a broken-down vehicle, an accident or other hazard.

Form: warning triangle (in full)
6. A right-angled triangular drawing instrument that is used for drawing lines, especially ones which are at 90°, 60°, 45° and 30°.

Etymology: 14c: from Latin triangulus three-cornered.