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
The three celestial bodies will appear to be within a degree of each other, forming an almost perfect straight-line alignment for some and a tight triangle for others, depending on location.
—
Jamie Carter, Forbes.com, 18 Sep. 2025
Hours after the series finale of the popular teen love triangle drama debuted Wednesday, news broke that Amazon has greenlit a feature film to conclude the YA story.
—Sydney Bucksbaum, Entertainment Weekly, 18 Sep. 2025
Briney’s Conrad and Belly getting back together, Briney is now in another love triangle — but this time for an audio erotica series.
—Lexy Perez, HollywoodReporter, 18 Sep. 2025
And therefore, b has to equal 0 (which isn’t interesting, because a triangle with one side whose length is zero is just a line) or 4.
—Ethan Siegel, Big Think, 18 Sep. 2025
See All Example Sentences for triangle
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Jamie Carter, Forbes.com, 18 Sep. 2025
Hours after the series finale of the popular teen love triangle drama debuted Wednesday, news broke that Amazon has greenlit a feature film to conclude the YA story.
—Sydney Bucksbaum, Entertainment Weekly, 18 Sep. 2025
Briney’s Conrad and Belly getting back together, Briney is now in another love triangle — but this time for an audio erotica series.
—Lexy Perez, HollywoodReporter, 18 Sep. 2025
And therefore, b has to equal 0 (which isn’t interesting, because a triangle with one side whose length is zero is just a line) or 4.
—Ethan Siegel, Big Think, 18 Sep. 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 22 Sep. 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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