What is the difference between a qualifier and a modifier in C?

Question

I would like to know the difference between a qualifier and a modifier. Some books suggest that volatile is a modifier, other books regard it as a qualifier.

So what is exactly a modifier and a qualifier, in respect to a variable?

Answer 1

In the C terminology volatile is a qualifier.

const, restrict, volatile and C11 _Atomic are the C type qualifiers.

C terminology does not use the word modifier when declaring an object.