sine
noun
ˈsīn 
1
: the trigonometric function that for an acute angle is the ratio between the leg opposite the angle when it is considered part of a right triangle and the hypotenuse
2
: a trigonometric function sin θ that for all real numbers θ is exactly equal to the sine of an angle of measure θ in radians and that is given by the sum of the alternating series {latex}\\sin \\theta = \\theta - \\frac{\\theta^{3}}{3!} + \\frac{\\theta^{5}}{5!} - \\frac{\\theta^{7}}{7!} + \\frac{\\theta^{9}}{9!} - \\dots{/latex}
Example Sentences
Recent Examples on the Web The answer: nothing. Remember that the basic trig functions (sine, cosine, tangent) are just ratios of sides of right triangles. 
Rhett Allain, Wired, 14 Mar. 2022 In 1807, Joseph Fourier discovered that any periodic function — an equation whose values repeat cyclically — could be expressed as the sum of trigonometric functions like sine and cosine. Quanta Magazine, 13 Oct. 2021 This geometric structure is closely connected to important ideas in trigonometry, like the angle sum and difference formulas for sine and cosine, the theory of rotations of the plane, and e, the base of the natural logarithm function. Quanta Magazine, 23 Sep. 2021 Markets move through something of a sine, cosine pattern from a seller’s market to a buyer’s market and back again. David Friedman, Forbes, 24 May 2021 The bigger this angle, the bigger the sine, and therefore the stronger their mutual influence. Quanta Magazine, 4 Apr. 2019 When a pair of arrows are coupled, the strength of their mutual influence depends on the sine of the angle between their pointing directions. Natalie Wolchover, WIRED, 7 Apr. 2019 See More
Rhett Allain, Wired, 14 Mar. 2022 In 1807, Joseph Fourier discovered that any periodic function — an equation whose values repeat cyclically — could be expressed as the sum of trigonometric functions like sine and cosine. Quanta Magazine, 13 Oct. 2021 This geometric structure is closely connected to important ideas in trigonometry, like the angle sum and difference formulas for sine and cosine, the theory of rotations of the plane, and e, the base of the natural logarithm function. Quanta Magazine, 23 Sep. 2021 Markets move through something of a sine, cosine pattern from a seller’s market to a buyer’s market and back again. David Friedman, Forbes, 24 May 2021 The bigger this angle, the bigger the sine, and therefore the stronger their mutual influence. Quanta Magazine, 4 Apr. 2019 When a pair of arrows are coupled, the strength of their mutual influence depends on the sine of the angle between their pointing directions. Natalie Wolchover, WIRED, 7 Apr. 2019 See More Word History
Etymology
Medieval Latin sinus, from Latin, curve
First Known Use
1593, in the meaning defined at sense 1