Hello, What would be a good definition of mechanical energy? I currently encounter the following two: 1) "Mechanical energy: energy that is mechanical" 2) "Mechanical energy: the sum of kinetic energy and potential energy." I am disatisfied with the first definition due to the obvious redundancy. I am disatisfied with the second definition because it seems obviously wrong to me. What about forms of kinetic energy and potential energy that are not mechanical (thermal, chemical, nuclear, etc)? How exactly do we define kinetic energy, potential energy, and mechanical energy to be consistent with each other and the world? If that second ME definition is truly appropriate, what am I mis-understanding? Also, a side question (possibly relevant to the questions above): How do we classify the energy carried by mechanical waves? How does the energy carried by mechanical waves relate to mechanical energy (if at all)?