Copied the following from "Grammarist"
Neither abbreviation is correct or incorrect. You may hear arguments for one being superior to the other, and there are logical cases for both sides. One could argue maths is better because mathematics ends in s, and one could argue math is better because mathematics is just a mass noun that happens to end in s. In any case, English usage is rarely guided by logic, and these usage idiosyncrasies are often arbitrary. If you were raised in a part of the world where people say maths, then maths is correct for you, and the same is of course true of math.