The same is true of "y" and "f(x)" (pronounced as "eff-of-eks"). For functions, the two notations mean the exact same thing, but "f(x)" gives you more flexibility and more information.

How do we go about evaluating functions? First, remember this: While parentheses have, up until now, always indicated multiplication (look back at that circumference formula in the last paragraph above), parentheses do not indicate multiplication in function notation. "f(x)" means "plug in a value for x"; it does not mean "multiply f and x"!