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adjective isos·ce·les \ī-ˈsäs-ˌlēz, -ˈsä-sə-\

Definition of isosceles

  1. 1 of a triangle :  having two equal sides — see triangle illustration

  2. 2 of a trapezoid :  having the two nonparallel sides equal

Origin and Etymology of isosceles

Late Latin isosceles having two equal sides, from Greek isoskelēs, from is- + skelos leg; perhaps akin to Old English sceol wry

First Known Use: 1551

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