I just read an article about the notations in mathematics. There are some articles like this one about the mathematical notations. Furthermore, here gives another further advise about writing.
In many places (textbooks, math contests, the questions here, etc.) we commonly use some fixed notations to represent some kinds of the variables (we limit the range of discussion in math forums or in math paper or some contexts like this, not including physics and other subjects.) For example, we commonly use $n$ to represent an integer, $p$ for a prime, $z$ for complex numbers, but we less likely use $n$ to represent a complex number or $z$ to represent a prime. So can I ask how this "regulation" formed or why do we have this common sense? I tried to find it in this stack exchange, but I can't find one... so I ask this question here.