triangular
Americanadjective
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Also: trigonal. of, shaped like, or relating to a triangle; having three corners or sides
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of or involving three participants, pieces, or units
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maths having a base shaped like a triangle
Other Word Forms
Etymology
Origin of triangular
1535–45; < Latin triangulāris, equivalent to triangul ( um ) triangle + -āris -ar 1
Explanation
Anything that looks like a a shape with three sides and three angles is triangular. If you see a triangular fin in the ocean while you’re swimming, watch out! Shark! Start looking for triangular shapes and you'll begin to see them everywhere, from a triangular slice of pizza to a tortilla chip. Like triangle, triangular is rooted in the Latin tri-, "three," and angulus, "angle or corner." You'll also occasionally find this adjective describing things that involve three people, like a triangular relationship between three best friends.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The fancy vivid blue-green diamond is triangular in shape and "the size of the nail on your smallest finger" according to Fawcett.
From Barron's • May 13, 2026
You will tape each end of the tail to where it matches the width of the triangular sections to make a connected long loop.
From Los Angeles Times • May 3, 2026
They are part of HS2's Delta junction, a complex triangular network of 13 viaducts, and will allow southbound trains to join the spur into Birmingham Curzon Street and the rolling stock depot at Washwood Heath.
From BBC • Apr. 16, 2026
At their point of contact, a large triangular slice of the addition is cut away, exposing the sides of the boxes and creating a street-level plaza.
From The Wall Street Journal • Mar. 20, 2026
Augustus slammed on the brakes, tossing me into the triangular embrace of the seat belt.
From "The Fault in Our Stars" by John Green
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
