What does sin in math mean?

Answer 1

sin is the abbreviation for sine, the trig ratio for a given angle of the opposite side over the hypotenuse of a right-angled triangle, (not much of an abbreviation, only one letter is dropped)
There are 3 primary ratios, and 3 reciprocal ratios
sin for sine, csc for cosecant
cos for cosine, sec for secant
tan for tangent, cot for cotangent

Answer 2

Thanks!!