People say that mathematics is a language. I agree, but...
One difficulty students have with the language of mathematics is that it uses words that have meanings the lie in the mathematical world as well as in the students' daily world.
Some quick examples: difference, product, plane, base, reciprocal, relation, similar, prime, over, left, real, imaginary, root, power, etc...
Plus, students need to know the multiple meanings of these words, discern which meaning is correct in a given context, and finally, understand and use the word as part of their communication process.
And teachers often get in the way by suggesting shortcuts. In word problems, an example is suggesting that the words "of" and "more" signal multiplication and addition situations respectively.
So, consider the problem: "Mr. More of Centerville had six more apples and he ate two of them...." Imagine the student's confusion!