Function notation

Question

What is f (q)?

Answer 1

This is function notation. It does not appear alone. It might be:

f(q) = 2q

creating the ordered pair (q, f(q))

Answer 2

Take the value of q, plug it into the function,

calculate the answer

Answer 3

It means function f in terms of q.  You can also say function f(x) when x=q.