TOTAL ENERGY OF A SYSTEM
The energy of a system (E) includes potential energy, kinetic energy, heat energy and any other type of energy, which the system possesses.
Total energy (E) of a molecule can be approximately presented as the sum of the electronic (Eel), oscillatory (Eosc) and rotatory (Erot) components:
E = Eel + Eosc + Erot,
where usually Eel >> Eosc >> Erot