(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
Geometry. (originally) a perpendicular line drawn from one extremity of an arc of a circle to the diameter that passes through its other extremity.
Mathematics. (of a real or complex number x ) the function sin x defined by the infinite series x − (x 3 /3!) + (x 5 /5!) − + …, where ! denotes factorial. Compare cosine ( def 2 ), factorial ( def 1 ).

1585–95; < Neo-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 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
sine1 (saɪn)
 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
[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]

sine2 (ˈsaɪnɪ)
(esp in Latin phrases or legal terms) lacking; without

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Word Origin & History

trigonometric function, 1593 (in Thomas Fale's "Horologiographia, the Art of Dialling"), from L. sinus "fold in a garment, bend, curve." Used by Gherardo of Cremona c.1150 in M.L. translation of Arabic geometrical text to render Arabic jiba "chord of an arc, sine" (from Skt. jya "bowstring"), which he
confused with jaib "bundle, bosom, fold in a garment."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
sine   (sīn)  Pronunciation Key 
  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.

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

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American Heritage
Abbreviations & Acronyms
sign, that is, operator's personal initials (shortwave transmission)
short interspersed elements
The American Heritage® Abbreviations Dictionary, Third Edition
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Published by Houghton Mifflin Company. All rights reserved.
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