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triangle

[trahy-ang-guh l]
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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. (initial capital letter) Astronomy. the constellation Triangulum.

Origin of triangle

1350–1400; Middle English < Latin triangulum, noun use of neuter of triangulus three-cornered. See tri-, angle1
Related formstri·an·gled, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for triangle

triangle

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 viewSee 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
Derived Formstriangled, adjective

Word Origin

C14: from Latin triangulum (noun), from triangulus (adjective), from tri- + angulus corner
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

Word Origin and History for triangle

n.

late 14c., from Old French triangle (13c.), from Latin triangulum "triangle," from neuter of adj. triangulus "three-cornered," from tri- "three" (see tri-) + angulus "corner, angle" (see angle (n.)).

In the huts of witches all the instruments and implements are triangular. ["Handwörterbuch des deutschen Aberglaubens"]
Online Etymology Dictionary, © 2010 Douglas Harper

triangle in Medicine

triangle

(trīăng′gəl)
n.
  1. A three-sided area, space, or structure.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

triangle in Science

triangle

[trīăng′gəl]
  1. A closed geometric figure consisting of three sides.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Idioms and Phrases with triangle

triangle

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