Sin refers to the trigonometric sine function, which relates angles in right triangles to ratios between sides. It returns the ratio between the length of the side opposite an angle and the hypotenuse.
Related terms
Trigonometry: The branch of mathematics that deals with relationships between angles and sides of triangles.
Cosine: Another trigonometric function that relates angles to ratios between adjacent sides and the hypotenuse.
Unit circle: A circle with a radius of 1 unit used to understand trigonometric functions in terms of coordinates on the circle.