Illustration of triangle
- 1 equilateral
- 2 acute
- 3 obtuse
- 4 scalene
- 5 isosceles
- 6 right triangle
triangle
noun
tri·an·gle
ˈtrī-ˌaŋ-gəl 
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
Examples of triangle in a Sentence
She cut the sandwiches into triangles.
Recent Examples on the Web
In the first video, Klum, 52, wears a terracotta brown two piece bikini that consists of a triangle top and matching bottoms.
—
Starr Bowenbank, People.com, 14 July 2025
Vega, the brightest star in the constellation Lyra, will be visible to its upper right, forming the apex of the triangle, while Altair — the most dazzling of the three stellar bodies — will twinkle to the lower right of the pair in the constellation Aquila.
—Anthony Wood, Space.com, 12 July 2025
The little triangle sounds fantastic and takes a real beating.
—Simon Hill, Wired News, 11 July 2025
Most of the park lies within Merton, but a small triangle falls into neighboring borough Wandsworth, which rejected the Wimbledon expansion.
—Tim Ellis, Forbes.com, 9 July 2025
See All Example Sentences for triangle
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Starr Bowenbank, People.com, 14 July 2025
Vega, the brightest star in the constellation Lyra, will be visible to its upper right, forming the apex of the triangle, while Altair — the most dazzling of the three stellar bodies — will twinkle to the lower right of the pair in the constellation Aquila.
—Anthony Wood, Space.com, 12 July 2025
The little triangle sounds fantastic and takes a real beating.
—Simon Hill, Wired News, 11 July 2025
Most of the park lies within Merton, but a small triangle falls into neighboring borough Wandsworth, which rejected the Wimbledon expansion.
—Tim Ellis, Forbes.com, 9 July 2025
See All Example Sentences for triangle
Cite this Entry
“Triangle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/triangle. Accessed 21 Jul. 2025.
Copy CitationKids Definition
triangle
noun
tri·an·gle
ˈtrī-ˌaŋ-gəl
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
: a three-sided region or space and especially an anatomical one see anterior triangle, carotid triangle, femoral triangle, posterior triangle, suboccipital triangle
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