Example1.1.16

The expression \(f(x)\) is read as “\(f\) of \(x\)”, and the expression \(f(2)\) is read as “\(f\) of \(2\)”. Be sure to practice saying this correctly while reading.

The expression \(f(2)\) means that \(2\) is being treated as an input, and the function \(f\) is turning it into an output. And then \(f(2)\) represents that actual output number.

in-context