# isosceles

## English

### Etymology

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

### Pronunciation

• IPA(key): /aɪˈsɒsəliːz/
•  Audio (Southern England): (file)

isosceles (not comparable)

1. (geometry) Having (at least) two sides of equal length, used especially of a triangle or trapezoid.
• 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:
Upon each exterior side draw an Isosceles Triangle of 480 Fathoms.
• 1914, Henry Parker Manning, Geometry of Four Dimensions, page 204:
A right double pyramid is isosceles when the extremities of the vertex-edge are at the same distance from the plane of the base.
• 1945, Harold E. Wolfe, Introduction to Non-Euclidean Geometry, page 31:
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.
• 1965 April 8, Newton B. Dismukes, “Multihull vessels (Patent US3316873A)”, in Google Patents[1]:
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.
• 2019 January 23, Altered Book Lover, “Funky Flowers”, in Blogspot[2]:
The flowers were stuck inside a flower pot that was shaped like an isosceles polygon with a rectangular "edge."

#### Usage notes

• A trapezoid with two equal sides and two unequal sides is normally described as unequilateral, even though it can be regarded as a special case of isosceles trapezoid.
• A triangle with three equal sides is normally described as equilateral, even though it can be regarded as a special case of isosceles triangle.

## Latin

### Etymology

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

### Pronunciation

• (īsoscelēs): IPA(key): /iːˈsos.ke.leːs/, [iːˈs̠ɔs̠kɛɫ̪eːs̠]
• IPA(key): /iˈsoʃ.ʃe.les/, [iˈs̬ɔʃːeles]
• (īsosceles): IPA(key): /iːˈsos.ke.les/, [iːˈs̠ɔs̠kɛɫ̪ɛs̠]
• IPA(key): /iˈsoʃ.ʃe.les/, [iˈs̬ɔʃːeles]

īsoscelēs (genitive īsoscelis); third-declension one-termination adjective

1. (geometry) isosceles (having equal legs)