What letters do different alphabets use for mathematical variables?

Greek:

Nick Nicholas’ answer to Do Greeks use Roman letters for serving the same purpose as the way we use Greek letters for different values of constants?

The very most you’ll see is High School algebra pretending x y are the Greek letters χ ψ through strategic use of Greek cursive.

On Greek cursive, see Nick Nicholas’ answer to Does an equivalent of cursive exist in other alphabets?

I actually don’t know if that extends in Greek high school to the third algebraic variable being omega. I doubt it.