internal energy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The sum of kinetic, potential, chemical, electrical, nuclear, and other energy associated with the atoms and molecules of a system. An increase in internal energy results in a rise in temperature or a change in phase.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics a property, characteristic of the state of a thermodynamic system, the change of which is equal to the heat absorbed minus the work done by the system