>>In what sense is the wave not reducible to the physical motion of the molecules? > >Generalized enough everything can be described as a transfer of energy. If you accept that 'transfer of energy' can serve as the definition of any process (wave, fire, typing comments on Reddit), then we are on the same page, and we now have universal and useless theory of everything. > >But if you insist that we cannot generalize like that because it omits important differences, then I repeat again: physical motion of the molecules is not a wave. Wave is a physical motion of the molecules in a pattern of wave.

What about "wave" is not reducible to the motion of the fluid particles?

Are you just saying that we have an abstract concept of a wave? Because that's true but pointless in the sense that we can't interact with abstract concepts, only physical realizations. There is no real wave which can be described exactly using abstract parameters associated with a general wave.