triangle
tri- + angle
https://gyazo.com/86c5869d11783f2782ef411c4cf24f63
source: Public Domain
noun
a plane figure with three straight sides and three angles:
三角形
e.g. an equilateral triangle.
a thing shaped like a triangle:
三角形の物.
e.g. a small triangle of grass.
a situation involving three people or things, especially an emotional relationship involving a couple and a third person with whom one of them is involved.
(男女の)三角関係(eternal triangle)
a musical instrument consisting of a steel rod bent into a triangle and sounded by being struck with a small steel rod.
〘楽〙 トライアングル〘三角形をした金属打楽器; → percussion 〙
a frame used to position the balls in pool and snooker.
North American a drawing instrument in the form of a right triangle.
｟米｠ 三角定規(｟英｠ set square)
(triangles) historical a frame of three halberds joined at the top to which a soldier was bound for flogging.
ORIGIN
late Middle English: from Old French triangle or Latin triangulum, neuter of triangulus ‘three-cornered’ (see tri-, angle1).