What does "sine" mean?

Sine: (a) The length of a perpendicular drawn from one extremity of an arc of a circle to the diameter drawn through the other extremity. (b) The perpendicular itself. See Sine of angle, below. Artificial sines, logarithms of the natural sines, or logarithmic sines. -- Curve of sines. See Sinusoid. -- Natural sines, the decimals expressing the values of the sines, the radius being unity. -- Sine of an angle, in a circle whose radius is unity, the sine of the arc that measures the angle; in a right-angled triangle, the side opposite the given angle divided by the hypotenuse. See Trigonometrical function, under Function. -- Versed sine, that part of the diameter between the sine and the arc.