The sine function, often abbreviated as sin, is a fundamental concept in trigonometry. It relates the angle of a right triangle to the ratio of the length of the opposite side to the hypotenuse. For any angle θ, the sine value can be calculated using the formula: sin(θ) = opposite/hypotenuse. This function is periodic, meaning it repeats its values in a regular pattern. In the context of the unit circle, the sine of an angle corresponds to the y-coordinate of a point on the circle. The sine function is widely used in various fields, including physics, engineering, and music, to model wave patterns and oscillations.