Definition of sine
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 a series of which the first term is θ and succeeding terms alternate in sign with the kth term being a fraction whose numerator consists of θ raised to the exponent 2k  1 and whose denominator is the factorial of 2k  1
Origin and Etymology of sine
Medieval Latin sinus, from Latin, curve
First Known Use: 1593
SINE Defined for English Language Learners
sine
playDefinition of sine for English Language Learners

geometry : the ratio between the long side (called the hypotenuse) and the side that is opposite to an acute angle in a right triangle
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Britannica English: Translation of sine for Arabic speakers Britannica.com: Encyclopedia article about sine
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