What is the scientific definition of "energy"?

looney_tunes

"In physics, energy (from the Greek ἐνέργεια - energeia, "activity, operation", from ἐνεργός - energos, "active, working") is a quantity that can be assigned to every particle, object, and system of objects as a consequence of the state of that particle, object or system of objects. Different forms of energy include kinetic, potential, thermal, gravitational, sound, elastic, light, and electromagnetic energy." http://en.wikipedia.org/wiki/Energy Many introductory textbooks define it as the ability to do work. But that leads to the circular definition of work as the action of changing the energy of an object. Apr 04 10, 9:03 PM