Maths is guilty of this. The way Maths is taught in school today is very common sense - children are encouraged to play around with numbers and experiment, and really understand what a particular Maths problem is about, and then use the way that seems most natural or common sense to them, to solve it. Children can and do use lots of different ways of adding up, subtracting, multiplying and dividing, which is why you may have heard terms such as the grid method, chunking, and the one my daughter brought home on a letter from school today - inverse operations. Basically, this idea involves turning the sum around. Subtraction is the inverse, or opposite, of addition, so if 3+1=4, then we know that 4-1=3. This works for multiplication and division too; multiplication is the inverse of division, so 3x2=6 and 6÷2=3.
The language that is used to teach Maths in school to our children may be different to that used when we were at school, but that doesn't mean that as parents we can't learn to speak it.