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

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

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

Danone BN 2.09%increase; green up pointing triangle booked a rise in like-for-like sales in the second quarter, bolstered by strong volume growth in the Asia-Pacific region.

From The Wall Street Journal ● Jul. 29, 2026

Ford Motor F 1.91%increase; up pointing triangle lifted its outlook as it now expects prices to be slightly higher this year.

From The Wall Street Journal ● Jul. 28, 2026

Caesars Entertainment CZR -0.07%decrease; down pointing triangle narrowed its quarterly loss as revenue edged higher, marking the company’s first earnings report since agreeing to be acquired by billionaire Tilman Fertitta in a $5.7 billion deal.

From The Wall Street Journal ● Jul. 28, 2026

Visa V 0.93%increase; green up pointing triangle is cutting 2,600 jobs, or about 7% of its workforce, as it works to adapt to the rapidly changing payments industry.

From The Wall Street Journal ● Jul. 28, 2026

If the stain were shaped like a circle, or like a square or a triangle, it would be easy to figure out; just take a ruler and measure its radius or its height and base.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

Mexico would use their two left-sided players to create dangerous triangles, not dissimilar to how England have played throughout the World Cup.

From BBC ● Jul. 6, 2026

England's third and fourth goals against Croatia were created through these wide triangles, but Ghana reduced this threat by matching them up three against three.

From BBC ● Jun. 24, 2026

For four points you can attach two equilateral triangles along an edge to make a diamond shape with five pairs of points the same distance from each other.

From Slate ● Jun. 22, 2026

McClung depicts the tower with rigid orange triangles and hints of dewy sun-kissed hues, alongside a pencil-drawn image of the old Mt.

From Los Angeles Times ● Apr. 9, 2026

Upstairs, Sisi had set eight places at the dining table, with wide plates the color of caramel and matching napkins ironed into crisp triangles.

From "Purple Hibiscus" by Chimamanda Ngozi Adichie

Related Words

• adultery
• affair
• courtship
• dalliance
• devotion
• fling
• flirtation
• infidelity
• involvement
• liaison
• love
• passion
• relationship
• tryst