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 figure was chosen because an American flag is folded thirteen times into a triangle shape during military funerals and other ceremonies to represent the thirteen colonies and stripes on the flag. Mike Dojc, Forbes, 18 Dec. 2024 This classic team-up of Bing Crosby and Fred Astaire follows the pair as musical entertainers in a love triangle with the same woman (Virginia Dale), resulting in them parting ways and Crosby's character creating the titular Holiday Inn. James Mercadante, EW.com, 17 Dec. 2024 Kitty is ready for a whole new school year — and new love triangles. Charna Flam, People.com, 17 Dec. 2024 For Southern Californians, also 45 minutes before the sun comes up that day, the crescent moon and Regulus will be to the left or lower left of Venus in a possible triangle shape. Karen Garcia, Los Angeles Times, 17 Dec. 2024 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

Dictionary Entries Near triangle

Cite this Entry

“Triangle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/triangle. Accessed 4 Jan. 2025.

Kids Definition

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

: 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

Last Updated: - Updated example sentences
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