Contracted from Latin complementi sinus 'sine of the complement,' coined by Edmund Gunter in 1620.
The trigonometric function equal to the ratio of the adjacent side to the hypotenuse in a right triangle.
Contraction of Latin complementi sinus 'sine of the complement,' because the cosine of an angle equals the sine of its complementary angle. Edmund Gunter coined the abbreviation 'co.sinus' in 1620, and it was later shortened to 'cosine.' Key roots: *sinus (Latin: "curve, fold, bay").
The entire chain from 'cosine' back to Sanskrit 'jyā' involves a spectacular mistranslation: Arab mathematicians confused the Sanskrit jīva ('bowstring') with jayb ('pocket'), and Latin translators then rendered jayb as sinus ('bay')—so 'sine' is the result of a double mistranslation.