- (of a straight-sided plane figure) having two sides equal: an isosceles triangle; an isosceles trapezoid.
Origin of isosceles
1545–55; < Late Latin < Greek isoskelḗs with equal legs, equivalent to iso- iso- + skél(os) leg + -ēs adj. suffix
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for isosceles
In an isosceles triangle the angles opposite the equal sides are equal.The Teaching of Geometry
David Eugene Smith
And equilaterals, and isosceles triangles, and all that, scoffed Neale.The Corner House Girls on a Tour
Grace Brooks Hill
So they crept up to the fire in the formation of an isosceles triangle.Denis Dent
Ernest W. Hornung
Then ask them if they are equal-legged (isosceles) triangles.Guide to the Kindergarten and Intermediate Class and Moral Culture of Infancy.
Elizabeth P. Peabody
That the angles at the base of an isosceles triangle are equal.A History of Science, Volume 1(of 5)
Henry Smith Williams
- (of a triangle) having two sides of equal length
- (of a trapezium) having the two nonparallel sides of equal length
C16: from Late Latin, from Greek isoskelēs, from iso- + skelos leg
Word Origin and History for isosceles
Online Etymology Dictionary, © 2010 Douglas Harper
- Of or relating to a geometric figure having at least two sides of equal length.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.