What does triangle mean?
A triangle is a geometric figure made from three straight sides and three angles. It can be equilateral, with all sides equal, isosceles, with two equal sides, or right-angled, with one angle of 90 degrees. Beyond geometry, triangle can mean a small metal percussion instrument shaped like an open triangle and struck with a beater. It also describes a group, arrangement, or relationship involving three people, objects, or factors: for example, a triangle of friendship among three colleagues or a strategic triangle between countries. The related adjective triangular is more common when describing an object that has a triangular shape, while triangulate and triangulation refer to measuring or determining positions by using triangles. Triangle is a neutral, precise word with both mathematical and figurative uses, and its geometric sense extends naturally into ideas of three-part relationships and balanced arrangements.
A closed plane figure with three straight sides and three angles; also, a metal percussion instrument shaped like an open triangle, or a group or arrangement of three related people or things.
"Draw a triangle inside the circle and label each angle."
The geometric sense is dominant. The musical-instrument and three-person relationship senses are also common in general English.
To arrange people, objects, or forces in a triangular formation.
"The defenders triangle across the entrance to the courtyard."
This verb is less common than the noun and is usually used in contexts involving military, sporting, or organized formations.
The standard plural is formed by adding -s to the noun.
"The diagram contains several overlapping triangles."
The word triangle comes from Latin and literally means a three-cornered shape, joining “three” to “angle” in its name.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does triangle come from?
English borrowed the word from Latin triangulus, meaning “three-cornered,” a form built from Latin tri-, meaning “three,” and angulus, meaning “angle.” The Latin word reflects the Greek trigōnon, “triangle,” which was likewise formed from elements meaning “three” and “angle.” The word became established in English during the Middle English period, and its modern scientific relatives include trigonometry and trigonometric.
Related word forms
How triangle is actually used
In ordinary use, triangle most often refers to a geometric shape or to three people or things connected in some way. The musical-instrument sense is formal but established. The verb is comparatively uncommon and usually describes arranging people or objects in a triangular formation.