isos·​ce·​les ī-ˈsä-sə-ˌlēz How to pronounce isosceles (audio)
of a triangle : having two equal sides see triangle illustration
of a trapezoid : having the two nonparallel sides equal

Examples of isosceles in a Sentence

Recent Examples on the Web Geographically, Richland, Hammonton, and Absecon don't form an isosceles triangle. Phil Anastasia,, 26 May 2017

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'isosceles.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from Late Latin isoscelēs, borrowed from Greek isoskelḗs "having equal legs, (of a triangle) having two equal sides, (of numbers) divisible into equal parts, even," from iso- iso- + -skelēs, adjective derivative of skélos (neuter s-stem) "leg," going back to an Indo-European base *skel- "bent," whence also Armenian šeł "slanting, crooked"; with o-grade, Greek skoliós "bent, crooked, askew, devious"; perhaps with a velar extension Germanic *skelga-/*skelha-, whence Old English sceolh "oblique, wry," Old Frisian skilich "squinting," Old High German skelah "crooked, oblique," Old Icelandic skjalgr "wry, oblique"

Note: The Indo-European etymon is also conventionally compared with Latin scelus "misfortune resulting from the ill will of the gods, curse, wicked or accursed act, crime, villainy," a neuter s-stem that appears to match exactly Greek skélos, though if "crime" is secondarily developed from a sense "misfortune," with religious connotations, a connection with crookedness is less likely.

First Known Use

1551, in the meaning defined at sense 1

Time Traveler
The first known use of isosceles was in 1551

Dictionary Entries Near isosceles

Cite this Entry

“Isosceles.” Dictionary, Merriam-Webster, Accessed 7 Dec. 2023.

Kids Definition


isos·​ce·​les ī-ˌsäs-(ə-)ˌlēz How to pronounce isosceles (audio)
: being a triangle with two equal sides
: being a trapezoid whose two nonparallel sides are equal

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