ETYM Late Lat. sinus a sine, Latin sinus bosom, used in translating the Arabic jaib, properly, bosom, but probably read by mistake (the consonants being the same) for an original jîba sine, from Skr. jîva bowstring, chord of an arc, sine.
(Homonym: sign) Ratio of the opposite side to the hypotenuse. In trigonometry, a function of an angle in a right-angled triangle which is defined as the ratio of the length of the side opposite the angle to the length of the hypotenuse (the longest side). Various properties in physics vary sinusoidally; that is, they can be represented diagrammatically by a sine wave (a graph obtained by plotting values of angles against the values of their sines). Examples include simple harmonic motion, such as the way alternating current (ac) electricity varies with time.

(Latin) “without”. sine die, “without a day or date”; indefinitely. sine mora, “without delay”. sine qua non, “without which not”; essential adjunct or condition.