(sīn) noun Trig.
1. A function of an angle in a right triangle expressible as the ratio of the side opposite the angle to the hypotenuse.
2. A function of any acute angle expressible, when plotted in Cartesian coordinates, as the ratio of the ordinate to the distance from the point where the ordinate crosses one leg of the angle to the origin. Abbreviated sin, as, sin A. See TRIGONOMETRIC FUNCTION.
—versed sine One of the trigonometric functions, equal to one minus the cosine: also versine. ♦ Homophone: sign. [<L sinus bend (trans. of Arabic jayb bosom of a garment, sine). Doublet of SINUS.]
SINE
AB. Arc.
AO. Radius.
BC. Perpendicular.
BC/AO is sine of the arc AB.

(sī′nē) prep. Latin
Without.