sine

Where does the word "sine" come from? It comes from Sanskrit jya, passing through Arabic and Latin before entering English (1590s).

Sine’s story begins in Sanskrit: jya meant “bowstring; chord of an arc.” Meant 'bowstring', used for the trigonometric chord of an arc. By medieval, the word had taken hold in Arabic as jiba. Arab mathematicians phonetically transliterated the Sanskrit term. By medieval, Arabic speakers had reshaped it into jaib. Later writers mistook 'jiba' for the real Arabic word 'jaib'. Latin picked it up next, as sinus, around 1150. Gherardo of Cremona translated the Arabic word by its Latin equivalent. It reached English by 1590s as sine. A Latin translator misread Arabic 'jiba' as 'jaib', fold or bay, and translated it 'sinus'. Today, sine means one of the three primary trigonometric functions, relating an angle of a right triangle to the ratio of its opposite side to the hypotenuse.

1. Stage 1 · Sanskrit · ancient jya "bowstring; chord of an arc", meant 'bowstring', used for the trigonometric chord of an arc.
2. Stage 2 · Arabic · medieval jiba "chord of an arc (a meaningless transliteration in Arabic)", Arab mathematicians phonetically transliterated the Sanskrit term.
3. Stage 3 · Arabic · medieval jaib "fold, bosom, bay", later writers mistook 'jiba' for the real Arabic word 'jaib'.
4. Stage 4 · Latin · 1150 sinus "a fold, curve, bay", Gherardo of Cremona translated the Arabic word by its Latin equivalent.
5. Stage 5 · English · 1590s sine "a fundamental trigonometric function", a Latin translator misread Arabic 'jiba' as 'jaib', fold or bay, and translated it 'sinus'.