noun \ˈtrī-ˌaŋ-gəl\

: a shape that is made up of three lines and three angles

: something that is shaped like a triangle

: a musical instrument that is made of a steel rod bent into the shape of a triangle and that you play by hitting with a metal rod

Full Definition of TRIANGLE

:  a polygon having three sides — compare spherical triangle
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
:  a situation in which one member of a couple is involved in a love affair with a third person

Examples of TRIANGLE

  1. She cut the sandwiches into triangles.

Illustration of TRIANGLE

Origin of TRIANGLE

Middle English, from Anglo-French, from Latin triangulum, from neuter of triangulus triangular, from tri- + angulus angle
First Known Use: 14th century


noun \ˈtrī-ˌaŋ-gəl\   (Medical Dictionary)

Medical Definition of TRIANGLE

: a three-sided region or space and especially an anatomical one—see anterior triangle, posterior triangle, scarpa's triangle, suboccipital triangle, superior carotid triangle


noun    (Concise Encyclopedia)

Geometric figure with three sides and three angles. Each two sides meet at a point called a vertex, and the three angles sum to 180°. A triangle with one 90° (right) angle is a right triangle. A triangle with all sides (and thus all angles) equal is equilateral, one with two sides equal is isosceles, and one with no two sides equal is scalene. Triangles are particularly useful in surveying, astronomy, and navigation. Two observation points (sight lines) form a triangle with a reference object serving as one vertex and the observation points as the other two. Knowing the angles of the sight lines and the distance between the observation points allows the calculation of the lengths of the other sides using the methods of trigonometry.


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