isosceles

Etymology

Borrowed from Latin īsoscelēs, from Ancient Greek ἰσοσκελής (isoskelḗs, “equal-legged”), from ἴσος (ísos, “equal”) + σκέλος (skélos, “leg”) + -ής (-ḗs, adjective suffix).

adj

1. (geometry) Having (at least) two sides of equal length, used especially of a triangle or trapezoid.
   Upon each exterior side draw an Isosceles Triangle of 480 Fathoms. 1693, Abel Swall, transl., The New Method of Fortification, as Practised by Monsieur de Vavban, Engineer General of France, 2nd edition, "A New Treatise of Fortification", page 96
   A right double pyramid is isosceles when the extremities of the vertex-edge are at the same distance from the plane of the base. 1914, Henry Parker Manning, Geometry of Four Dimensions, page 204
   To prepare for the application of his method, Saccheri made use of a figure with which we are already acquainted. This is the isosceles quadrilateral with the two base angles right angles. 1945, Harold E. Wolfe, Introduction to Non-Euclidean Geometry, page 31
   The polygon advantageously is an isosceles trapezoid or rectangle with the pivotal connections between the deck or superstructure and four hulls respectively at its corners. 1965-04-08, Newton B. Dismukes, “Multihull vessels (Patent US3316873A)”, in Google Patents
   The flowers were stuck inside a flower pot that was shaped like an isosceles polygon with a rectangular "edge." 23 January 2019, Altered Book Lover, “Funky Flowers”, in Blogspot