The sine function is a fundamental mathematical function that relates the angle of a right triangle to the ratio of the length of the opposite side to the hypotenuse. It is commonly denoted as sin(θ), where θ represents the angle. The sine function is periodic, meaning it repeats its values in regular intervals, specifically every 360 degrees or 2π radians. In the context of the unit circle, the sine function can also be understood as the y-coordinate of a point on the circle corresponding to a given angle. This makes it useful in various fields, including trigonometry, physics, and engineering, where it helps model oscillatory motions and waves.