[ sahyn ]

  1. Trigonometry.

    • (in a right triangle) the ratio of the side opposite a given acute angle to the hypotenuse.

    • (of an angle) a trigonometric function equal to the ratio of the ordinate of the end point of the arc to the radius vector of this end point, the origin being at the center of the circle on which the arc lies and the initial point of the arc being on the x-axis. Abbreviation: sin

  2. Geometry. (originally) a perpendicular line drawn from one extremity of an arc of a circle to the diameter that passes through its other extremity.

  1. Mathematics. (of a real or complex number x) the function sin x defined by the infinite series x − (x3/3!) + (x5/5!) − + …, where ! denotes factorial.: Compare cosine (def. 2), factorial (def. 1).

Origin of sine

1585–95; <New Latin, Latin sinus a curve, fold, pocket, translation of Arabic jayb literally, pocket, by folk etymology <Sanskrit jiyā, jyā chord of an arc, literally, bowstring

Words Nearby sine Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use sine in a sentence

British Dictionary definitions for sine (1 of 2)


/ (saɪn) /

noun(of an angle)
  1. : Abbreviation: sin

    • a trigonometric function that in a right-angled triangle is the ratio of the length of the opposite side to that of the hypotenuse

    • 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

Origin of sine

C16: 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

British Dictionary definitions for sine (2 of 2)


/ (ˈsaɪnɪ) /

  1. (esp in Latin phrases or legal terms) lacking; without

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for sine


[ sīn ]

  1. The ratio of the length of the side opposite an acute angle in a right triangle to the length of the hypotenuse.

  2. The ordinate of the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of length x and measured counterclockwise from the point (1, 0) if x is positive or clockwise if x is negative.

  1. A function of a number x, equal to the sine of an angle whose measure in radians is equal to x.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.