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.
And on the top right are the inhibitory emotions — emotions like anxiety, shame and guilt; their job is to push down our core emotions, which are at the bottom of the triangle. CNN Money, 25 Sep. 2025 As the deceased mother of Conrad and Jeremiah and pseudo-auntie to Belly Conklin, Susannah haunts season three’s love triangle heavily, to the point that after Belly and Conrad hook up in the finale, Belly’s first postcoital thoughts aren’t about the love of her life but his mom. Bethy Squires, Vulture, 25 Sep. 2025 So dark but for a splash of moon in the triangle window that made everything a little silvery. Literary Hub, 24 Sep. 2025 As with Passion, power plays a central role in this tale of a royal bisexual love triangle. Mathew Rodriguez, Them., 23 Sep. 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 1 Oct. 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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