tri·​an·​gle | \ ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio) \

Definition of triangle

1 : a polygon having three sides — compare spherical triangle
2a : 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

Illustration of triangle

triangle 1: 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 Jed Wyatt had been following Tyler Cameron‘s love triangle with his ex Hannah Brown and supermodel Gigi Hadid. Karen Mizoguchi,, "Bachelorette's Jed Wyatt Reacts to Hannah Brown, Tyler Cameron & Gigi Hadid Love Triangle," 8 Sep. 2019 September 5 Look towards the southern sky for an eye-catching celestial triangle this evening, formed by the first-quarter moon, Jupiter, and the 550 light-year distant star Antares. Andrew Fazekas, National Geographic, "See Neptune at its best and more top stargazing in September," 1 Sep. 2019 Its detectors will be arranged in an equilateral triangle with sides 2.5m kilometres long. The Economist, "Gravitational astronomy proves its maturity," 22 Aug. 2019 And then there is Remus’ wife, who fell in love with the federal agent responsible for landing him behind bars, sparking a love triangle with deadly repercussions. Catalina Righter,, "Trio of bestselling authors to visit Carroll County in August: Sandra Brown, CJ Box, Karen Abbott," 30 July 2019 The New Dean Once upon a time, Dean got himself in trouble by entering a Paradise love triangle with Danielle and Kristina. Martha Sorren,, "The Bachelor In Paradise 2019 Trailer Is Here: It's Got Demi's Love Triangle, New Cast & So Much More," 25 July 2019 Part of that movement includes the show’s many beloved ships: Sutton and company executive Richard Hunter, Kat and Adena, and Jane’s love triangle with Dr. Ben and Pinstripe. Claire Dodson, Teen Vogue, ""The Bold Type" Stars Aisha Dee, Meghann Fahy, and Katie Stevens Talk What to Expect in Season 3," 11 Apr. 2019 The Devil's eyebrows and goatee are fake fur and the horns are felt triangles. Michele Filon, Woman's Day, "Witch-Craft Meets Delightful Devil," 9 Sep. 2019 This season, however, a simple triangle would be quaint. Lisa Bonos, Washington Post, "How Blake Horstmann on ‘Bachelor in Paradise’ became the center of a ‘love pentagon’," 13 Aug. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'triangle.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of triangle

14th century, in the meaning defined at sense 1

History and Etymology for triangle

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

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Statistics for triangle

Last Updated

23 Oct 2019

Time Traveler for triangle

The first known use of triangle was in the 14th century

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How to pronounce triangle (audio)

English Language Learners Definition of triangle

: a shape that is made up of three lines and three angles
: something that is shaped like a triangle
: a musical instrument that is made of a steel rod bent into the shape of a triangle and that you play by hitting with a metal rod


tri·​an·​gle | \ ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio) \

Kids Definition of triangle

1 : a flat geometric figure that has three sides and three angles
2 : something that has three sides and three angles a triangle of land
3 : a musical instrument made of a steel rod bent in the shape of a triangle with one open angle


tri·​an·​gle | \ ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio) \

Medical Definition of triangle

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

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More from Merriam-Webster on triangle

Rhyming Dictionary: Words that rhyme with triangle

Spanish Central: Translation of triangle

Nglish: Translation of triangle for Spanish Speakers

Britannica English: Translation of triangle for Arabic Speakers Encyclopedia article about triangle

Comments on triangle

What made you want to look up triangle? Please tell us where you read or heard it (including the quote, if possible).


to spread as a report or rumor

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