Here is an example of something you will find when you study quantum mechanics. It is called Schrodinger’s Equation and it describes how the “quantum state” of a physical system (ie. a particle) changes over time. This is a wave equation and it works because all matter in the universe has both particle and wave duality. In other words, sometimes matter behaves like a particle (that’s where Newton’s equations come in handy) and sometimes it behaves like a wave in which case we use some sort of wave equation like the one we have here.