We begin with an imperfect verbal definition of physics:

Physics is a way of studying the observable universe.  It consists of precise, accurate, and controlled measurements of naturally-occurring phenomena, and logically-consistent (in theory anyway) mathematical models of those measurements. When the measured value and the calculated value are equal to within experimental uncertainty, that is what we refer to, rather valiantly, as “scientific truth.” This doesn’t mean that some future more precise measurement won’t change the situation. In fact, it is all but certain that some future scientific result will expand on or even contradict in some sense what we have now. It does mean that design engineers can, for the moment anyhow, bank on things occurring that way, at least up to the numerical limits specified in those physical calculations and measurements. So physics underlies engineering, yes, even chemical engineering, and math underlies physics. As Godel has disabused Russell, Whitehead and the rest of us of trying to slide “logic” underneath “mathematics,” it looks like the bottom of the structure is math, or maths, as you should say in the mother tongue.