Jawaher’s Reviews > How to Think Like a Mathematician: A Companion to Undergraduate Mathematics > Status Update

“Another example is that you should distinguish between a function and its value at a
point, that is, between f and f(x). The first represents a function which we have called
f, while f(x)is the value of the function f at x(see page 10). Strictly speaking, you
should not call f(x)a function, but this distinction is often ignored by mathematicians
who should know better (and that includes me)”