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triangle

American  
[trahy-ang-guhl] / ˈtraɪˌæŋ gəl /

noun

  1. a closed plane figure having three sides and three angles.

  2. a flat triangular piece, usually of plastic, with straight edges, used in connection with a T square for drawing perpendicular lines, geometric figures, etc.

  3. any three-cornered or three-sided figure, object, or piece.

    a triangle of land.

  4. a musical percussion instrument that consists of a steel triangle, open at one corner, that is struck with a steel rod.

  5. a group of three; triad.

  6. a situation involving three persons, especially one in which two of them are in love with the third.

  7. Astronomy. Triangle, the constellation Triangulum.

triangle British  
/ ˈtraɪˌæŋɡəl /

noun

  1. geometry a three-sided polygon that can be classified by angle, as in an acute triangle, or by side, as in an equilateral triangle. Sum of interior angles: 180°; area: 1/ 2 base × height

  2. any object shaped like a triangle

  3. any situation involving three parties or points of view See also eternal triangle

  4. music a percussion instrument consisting of a sonorous metal bar bent into a triangular shape, beaten with a metal stick

  5. a group of three

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
triangle Scientific  
/ trī′ăng′gəl /

  1. A closed geometric figure consisting of three sides.

triangle Idioms  

  1. see eternal triangle.

Other Word Forms

  • triangled adjective

Etymology

Origin of triangle

First recorded in 1350–1400; Middle English, from Latin triangulum, noun use of neuter of triangulus “three-cornered”, tri-, angle 1

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Disney DIS 3.55%increase; green up pointing triangle is preparing to make sizable layoffs in one of the first significant moves under the new chief executive officer, Josh D’Amaro.

From The Wall Street Journal • Apr. 9, 2026

BlackRock BLK 4.49%increase; green up pointing triangle went on an acquisition spree in the past few years to juice its growth in private markets, Wall Street’s hottest area.

From The Wall Street Journal • Apr. 9, 2026

Hong Kong conglomerate CK Hutchison 1 3.54%increase; green up pointing triangle has started arbitration against A.P.

From The Wall Street Journal • Apr. 8, 2026

Each time the stock bounced off $10, a bearish descending triangle formed.

From Barron's • Apr. 8, 2026

In particular, notice that some symbols, such as the 11minus11 sign and the triangle, can refer to different chords, depending on the assumptions of the person who wrote the symbol.

From "Understanding Basic Music Theory" by Catherine Schmidt-Jones and Russel Jones

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.