I have read in different places that an up to date definition of energy refers to the Lagrangian and Noether. But isn't the Lagrangian too limited because it refers to an ideal situation involving translational KE and to PE only? I would have thought that a good definition of energy would be relevant to all forms of energy....electrical, chemical, radiant, heat etc. I think I may be missing something. If so can somebody tell me what it is please? Thank you.