a. a trigonometric function that in a right-angled triangle is the ratio of the length of the opposite side to that of the hypotenuse
b. a function that in a circle centred at the origin of a Cartesian coordinate system is the ratio of the ordinate of a point on the circumference to the radius of the circle Abbreviation sin
[from Latin sinus a bend; in New Latin, sinus was mistaken as a translation of Arabic jiba sine (from Sanskrit jīva, literally: bowstring) because of confusion with Arabic jaib curve]