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 2002 movie Rules of Attraction introduced a darker side to Van Der Beek, as Sean Bateman, a drug dealer and the younger brother of American Psycho’s Patrick Bateman, who is caught in a love triangle with a virgin and her bisexual ex-boyfriend.
—
Ale Russian, Rolling Stone, 11 Feb. 2026
Their uneasy dynamic fractures when the attorney embarks on a consuming affair with a younger woman, igniting a volatile love triangle that unleashes obsession, betrayal and a ruthless battle for control of the family fortune.
—Matt Grobar, Deadline, 10 Feb. 2026
The truck had parked on the shoulder due to a mechanical failure, and had deployed emergency warning triangles behind the trailer before the crash.
—Todd Feurer, CBS News, 10 Feb. 2026
Our fellow guests were all seated at garden tables, nibbling sandwiches cut into little triangles and sipping from fancy teacups.
—Flora Stubbs, Travel + Leisure, 7 Feb. 2026
See All Example Sentences for triangle
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Ale Russian, Rolling Stone, 11 Feb. 2026
Their uneasy dynamic fractures when the attorney embarks on a consuming affair with a younger woman, igniting a volatile love triangle that unleashes obsession, betrayal and a ruthless battle for control of the family fortune.
—Matt Grobar, Deadline, 10 Feb. 2026
The truck had parked on the shoulder due to a mechanical failure, and had deployed emergency warning triangles behind the trailer before the crash.
—Todd Feurer, CBS News, 10 Feb. 2026
Our fellow guests were all seated at garden tables, nibbling sandwiches cut into little triangles and sipping from fancy teacups.
—Flora Stubbs, Travel + Leisure, 7 Feb. 2026
See All Example Sentences for triangle
Cite this Entry
“Triangle.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/triangle. Accessed 14 Feb. 2026.
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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