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}

Examples of sine in a Sentence

Recent Examples on the Web

These approaches rely on mathematical functions like squaring, adding, or multiplying, rather than irrational numbers, radicals, or functions like sine and cosine. —Jack Beresford, MSNBC Newsweek, 1 May 2025

Housed in a steel chassis, the motor incorporates a programmable microprocessor with a D/A converter to provide low-distortion sine and cosine waves that are used to turn the motor. —Mark Sparrow, Forbes.com, 11 Apr. 2025

Where previously players could only activate one effect at a time, up to four effects can now sound simultaneously – with users able to choose from chorus, vibrato, flanger, delay (with tap tempo), reverb (acoustic, hall or plate) and tremolo (sine/triangle) out of the box. —Paul Ridden, New Atlas, 7 Oct. 2024

Six hundred years ago, mathematicians were building tables of sines and cosines, which were needed for navigation, but these can now be generated by computers in seconds. —Matteo Wong, The Atlantic, 4 Oct. 2024

Word History

Etymology

Medieval Latin sinus, from Latin, curve

First Known Use

1593, in the meaning defined at sense 1

Phrases Containing sine

• arc sine
• sine curve
• sine die
• sine qua non
• sine wave

Rhymes for sine

• brine
• cline
• dine
• fein
• fine
• gwine
• hine
• jain
• klein
• kline
• line
• mine

Kids Definition

sine

noun

ˈsīn 

: a trigonometric function that for an acute angle in a right triangle is the ratio of the side opposite the angle to the hypotenuse