I want to use a symbol f in some of my equations (to denote a very important function), and I want it to stand out, so I was thinking of boosting its size. Unfortunately, I cannot find a way of enlarging particular parts within an equation, as opposed to enlarging an equation as a whole (with, for instance, \scaleboxfrom graphicx package) or shrinking a particular part (with, for instance, \scriptsize of mathtools). Of course, I could make a separate equation for every f, but this would be quite messy in practice, and it is hard to phrase as a \newcommand (and I definitely want a \newcommand{\f} for this).
So, is there a way I can go about obtaining the enlarged f in math mode?
