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
Earlier in the day, authorities released new images of the suspect wearing a black T-shirt with an American flag with an eagle on it, a hat with a triangle on it, sunglasses, and a black backpack.
—
Will Carless, USA Today, 11 Sep. 2025
Instead of the old-school triangle eyes and jagged mouth designs, this year's top trends are all about mixing tradition with fresh tools and vibrant colors.
—Maria Sabella, Better Homes & Gardens, 10 Sep. 2025
What are the theories about the triangle?
—Jenna Prestininzi, Freep.com, 10 Sep. 2025
The area is a rough triangle bounded by the 12th Street viaduct to the south, the Union Pacific Railroad tracks to the north, Santa Fe Street to the east and Liberty Street to the west.
—Eric Adler, Kansas City Star, 10 Sep. 2025
See All Example Sentences for triangle
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Will Carless, USA Today, 11 Sep. 2025
Instead of the old-school triangle eyes and jagged mouth designs, this year's top trends are all about mixing tradition with fresh tools and vibrant colors.
—Maria Sabella, Better Homes & Gardens, 10 Sep. 2025
What are the theories about the triangle?
—Jenna Prestininzi, Freep.com, 10 Sep. 2025
The area is a rough triangle bounded by the 12th Street viaduct to the south, the Union Pacific Railroad tracks to the north, Santa Fe Street to the east and Liberty Street to the west.
—Eric Adler, Kansas City Star, 10 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 14 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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