triangle

American  

[trahy-ang-guhl] / ˈtraɪˌæŋ gəl /

noun

• triangles
  plural

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.

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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

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triangle Scientific  

/ trī′ăng′gəl /

1. A closed geometric figure consisting of three sides.

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triangle Idioms  

1. see eternal triangle.

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Other Word Forms

Derived Forms

• triangled
  adjective

Inflected Forms

Nouns

• triangles
  plural

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Etymology

Origin of triangle

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

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Explanation

A triangle is a flat shape with three sides and three angles, like a slice of pizza, a yield sign, or the Greek letter delta. If you look carefully, you'll notice triangles all around you! A triangle is a polygon, which is a closed shape like a square or a hexagon, but a triangle has only three sides. Wedges of pie and some tortilla chips are shaped like triangles. If you invite your crush to a movie and they bring a date, you have yourself a love triangle. Triangle comes from the Latin word triangulus, "three-cornered" or "having three angles," from the roots tri-, "three," and angulus, "angle or corner."

Example Sentences

See Examples For:

triangle triangles

DHL Group DHL 0.90%increase; up pointing triangle upgraded its outlook for 2026 on the back of positive momentum and prospects of a strong seasonal peak in the last quarter of the year.

From The Wall Street Journal ● Oct. 16, 2026

Natural-gas exporter Venture Global VG -4.12%decrease; down pointing triangle is joining the race to provide power to the AI boom, aiming to build gas-fired generation at its facilities to supply electricity to data centers.

From The Wall Street Journal ● Oct. 15, 2026

Luxury-fashion company Brunello Cucinelli BC 0.63%increase; up pointing triangle again lifted its sales expectations for the full year on the back of continued momentum, contrasting with lackluster performance elsewhere in Europe’s luxury-goods sector.

From The Wall Street Journal ● Oct. 15, 2026

With six consecutive quarters of record earnings, TSMC’s 2330 -2.01%decrease; down pointing triangle already twice-improved 2026 revenue growth outlook of “slightly above 40%” in dollar terms now looks conservative and due for another upgrade.

From The Wall Street Journal ● Oct. 15, 2026

The waving man at the peak of the right triangle is the climax of this mood of rising hope and advancing motion.

From "The Annotated Mona Lisa" by Carol Strickland and John Boswell

Small triangles would behave almost exactly as Euclid predicted, and short parallel paths would not noticeably converge.

From Science Daily ● Sep. 28, 2026

They do not do this in fixed zones but look to create these triangles when they feel like the moment is right.

From BBC ● Sep. 13, 2026

Another young adult drama debuting later this year is “Minimum Wage,” which focuses on teens managing part-time jobs and love triangles.

From Los Angeles Times ● Aug. 14, 2026

With Argentina in the semi-finals, a team that have shown vulnerabilities out wide, he will undoubtedly remain fixated on getting his wide triangles to work.

From BBC ● Jul. 12, 2026

That square was bordered with sawtoothed triangles, forming smaller squares.

From "Hattie Big Sky" by Kirby Larson

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