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[ee-kwuh-lat-er-uh l, ek-wuh-]
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  1. having all the sides equal: an equilateral triangle.
  1. a figure having all its sides equal.
  2. a side equivalent, or equal, to others.

Origin of equilateral

From the Late Latin word aequilaterālis, dating back to 1560–70. See equi-, lateral
Related formse·qui·lat·er·al·ly, adverbnon·e·qui·lat·er·al, adjectivenon·e·qui·lat·er·al·ly, adverbsub·e·qui·lat·er·al, adjectiveun·e·qui·lat·er·al, adjectiveun·e·qui·lat·er·al·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for equilateral


  1. having all sides of equal lengthan equilateral triangle
  1. a geometric figure having all its sides of equal length
  2. a side that is equal in length to other sides
Derived Formsequilaterally, adverb
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for equilateral


1560s, from Late Latin aequilateralis, from aequi- (see equal (adj.)) + lateralis (see lateral).

Online Etymology Dictionary, © 2010 Douglas Harper

equilateral in Science


  1. Having all sides of equal length, as a triangle that is neither scalene nor isosceles.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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