Why is the degree of a variable 0

If I have a term
x
why is it's degree zero rather than 1?

Is x being treated as a constant variable?

The degree of x is 1 not 0.
The degree is the highest power of a variable.
Since you have only x and its power is 1, its degree is 1

I'm not sure where the question comes from, are thinking it or were you told it? The degree of x IS 1, not 0.

A constant term has degree zero, as you said. It is not usual convention to use x to represent a constant term.