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tri·an·gle (trīăng′gəl)
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n.
1.
a. The plane figure formed by connecting three points not in a straight line by straight line segments; a three-sided polygon.
b. Something shaped like such a figure: a triangle of land.
2. Any of various flat, three-sided drawing and drafting guides, used especially to draw straight lines at specific angles.
3. Music A percussion instrument consisting of a piece of metal in the shape of a triangle open at one angle.
4. A relationship involving three people, especially a ménage à trois.
[Middle English, from Old French, from Latin triangulum, from neuter of triangulus, three-angled : tri-, tri- + angulus, angle.]
(click for a larger image)
triangle
top: right triangle
bottom: equilateral triangle
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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