My issue is what constitutes "different" since shm is all the same? Aren't they all isomorphic to each other? Then they are not different. Also everywhere I read someone is talking about shm and then they deviate and then I am not sure where they began to deviate. For example I know that shm is periodic and that the frequency is constant. The velocity of the oscillator is maximum as it passes thorgh equilibrium and zero as it passes through the extreme positions in it's oscillation. I know there is always a restoring force which always acts toward the equilibrium position. The acceleration is directly proportional to the displacement from the equilibrium position. So you see I have done my homework. I know shm is in springs, pendulums, waves, molecules, Lc circuits. I just wanted to know more than that and how to discern when a writer has deivated from shm, that's all. And oh yeah, I am a graduate student and this is paper I am researching so it's not homework. PS Your spell check is not working, blank screen that says it is done.