sine

American  

[sahyn] / saɪn /

noun

1. Trigonometry.

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

   2. (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. 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.

3. Mathematics. (of a real or complex numberx ) the function sin x defined by the infinite series x − (x 3 /3!) + (x 5 /5!) − + …, where ! denotes factorial.

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sine ¹ British  

/ ˈsaɪnɪ /

preposition

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

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sine ² British  

/ saɪn /

noun

1.  sin. 

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

   2. 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

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sine Scientific  

/ 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.

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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Etymology

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

Example Sentences

In fact, the history of whaling on its own disproves the central point of “The Killing Age,” that guns were a sine qua non for the making of the modern world.

From The Wall Street Journal • Nov. 14, 2025

Glasnow has been out sine April 28 with shoulder discomfort.

From Los Angeles Times • Jul. 6, 2025

He talks a lot about what you just mentioned, which is the sort of sine curve of public interest in surveillance.

From Salon • Aug. 21, 2024

But a first hostage deal “is the sine qua non of the administration’s larger regional deal,” said Martin S. Indyk, a former U.S. ambassador to Israel.

From New York Times • Jan. 25, 2024

I sometimes dreamed about sine, cosine and tangent, about mysterious angles and concussed computations, but for all this I made no real progress.

From "Educated" by Tara Westover