triangle

noun

tri·​an·​gle ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio)
1
: a polygon having three sides compare spherical triangle
2
a
: 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
  • 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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The third and final side of the triangle is a cruise along the A16 Highway through bucolic countryside to Vilnius. Joe Yogerst, Forbes.com, 22 Apr. 2025 What does the future hold in this interesting triangle? Ronda Racha Penrice, HollywoodReporter, 17 Apr. 2025 Related Articles The event is aimed at promoting the Celine summer collection, which includes raffia baskets, small leather goods, ready-to-wear, accessories and lifestyle items featuring French summery decorative elements such as a triangle bag carrying three metal Pétanque balls. Tianwei Zhang, Footwear News, 10 Apr. 2025 The swimsuit featured gold chain-link details connecting the triangle top and in place of where strings would go for the bikini's bottom. Starr Bowenbank, People.com, 10 Apr. 2025 See All Example Sentences for triangle

Word History

Etymology

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

First Known Use

14th century, in the meaning defined at sense 1

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

Browse Nearby Words

Cite this Entry

“Triangle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/triangle. Accessed 26 Apr. 2025.

Kids Definition

triangle

noun
tri·​an·​gle ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio)
1
: a figure that has three sides and three angles : a polygon that has three sides
2
: a percussion instrument made of a steel rod bent into a triangle open at one corner which is played by striking with a metal rod
3
: a drafting instrument consisting of a thin flat right-angled triangle

Medical Definition

triangle

noun
tri·​an·​gle ˈtrī-ˌaŋ-gəl How to pronounce triangle (audio)
: a three-sided region or space and especially an anatomical one see anterior triangle, carotid triangle, femoral triangle, posterior triangle, suboccipital triangle

More from Merriam-Webster on triangle

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