Cartwright, Nancy - How the Laws of Physics Lie

Philosophers distinguish phenomenological from theoretical laws. Phenomenological laws are about appearances; theoretical ones are about the reality behind the appearances. The distinction is rooted in epistemology. Phenomenological laws are about things which we can at least in principle observe directly, whereas theoretical laws can be known only by indirect inference. Normally for philosophers 'phenomenological' and 'theoretical' mark the distinction between the observable and the unobservable.

Physicists also use the terms 'theoretical' and 'phenomenological'. But their usage makes a different distinction. Physicists contrast 'phenomenological' with 'fundamental'.