triangle

noun

tri·​an·​gle ˈtrī-ˌaŋ-gəl 

1

: a polygon having three sides compare spherical triangle

2

a

: a percussion instrument consisting of a rod of steel bent into the form of a triangle open at one angle and sounded by striking with a small metal rod

b

: a drafting instrument consisting of a thin flat right-angled triangle of wood or plastic with acute angles of 45 degrees or of 30 degrees and 60 degrees

3

: a situation in which one member of a couple is involved in a love affair with a third person

Illustration of triangle

• 1 equilateral
• 2 acute
• 3 obtuse
• 4 scalene
• 5 isosceles
• 6 right triangle

Examples of triangle in a Sentence

She cut the sandwiches into triangles.

Recent Examples on the Web

Dip fingertip into flour mixture, and moisten wrapper down the left side of the triangle. —Sabrina Weiss, People.com, 4 Nov. 2024

Jason Bateman and David Harbour will star in and executive produce a seven-episode series on HBO titled DTF St. Louis, the tale of a love triangle between three adults experiencing middle-age uneasiness that leads to one of them ending up dead. —Marc Berman, Forbes, 2 Nov. 2024

There’s a friendship triangle taking shape, as Simone and Pita grow closer, shutting Gigi out. —Doreen St. Félix, The New Yorker, 2 Nov. 2024

Francis Ford Coppola goes kinky gothic delicious for this classic tale of the Prince of Darkness/Jonathan Harker/Mina love triangle featuring Gary Oldman, Keanu Reeves, and Winona Ryder as its leads. —Jordan Crucchiola, Vulture, 29 Oct. 2024

Word History

Etymology

Middle English, from Anglo-French, from Latin triangulum, from neuter of triangulus triangular, from tri- + angulus angle

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing triangle

• equilateral triangle
• isosceles triangle
• Pascal's triangle
• right-angled triangle
• right triangle
• spherical triangle
• triangle inequality

Kids Definition

triangle

noun

tri·​an·​gle ˈtrī-ˌaŋ-gəl 

1

: a figure that has three sides and three angles : a polygon that has three sides

2

: a percussion instrument made of a steel rod bent into a triangle open at one corner which is played by striking with a metal rod

3

: a drafting instrument consisting of a thin flat right-angled triangle

Medical Definition

triangle

noun

tri·​an·​gle ˈtrī-ˌaŋ-gəl 

: a three-sided region or space and especially an anatomical one see anterior triangle, carotid triangle, femoral triangle, posterior triangle, suboccipital triangle