Number & MeasureGreek → English
Isosceles
/aɪˈsɒsɪliːz/adjective
Having two sides of the same length, said of a triangle.
The Greek roots
ἴσος
ísos
equal
σκέλος
skélos
leg
Literally: “equal-legged”
The story of the word
σκέλος is the leg you walk on, so the triangle is equal-legged rather than equal-sided. Euclid uses ἰσοσκελές in precisely the modern sense, and the word reached English geometry in the 16th century without a scratch. The same leg turns up in triskelion, the three-legged emblem of Sicily and the Isle of Man.
- How it travelled
- Ancient Greek → Latin → English
- First recorded
- 16th century
Same family
isobarisotopeisomertriskelion
In a sentence
Fold the square along the diagonal and you get two isosceles triangles.