en·er·gy
[en-er-jee]

–noun, plural -gies.
1.the capacity for vigorous activity; available power: I eat chocolate to get quick energy.

2. an adequate or abundant amount of such power: I seem to have no energy these days.

3. Often, energies. a feeling of tension caused or seeming to be caused by an excess of such power: to work off one’s energies at tennis.

4. an exertion of such power: She plays tennis with great energy.

5. the habit of vigorous activity; vigor as a characteristic: Foreigners both admire and  laugh at American energy.

6. the ability to act, lead others, effect, etc., forcefully.

7. forcefulness of expression: a writing style abounding with energy.

8. Physics . the capacity to do work; the property of a system that diminishes when the system does work on any other system, by an amount equal to the work so done; potential energy . Symbol:   E

9. any source of usable power, as fossil fuel, electricity, or solar radiation.

—Synonyms
1.   vigor, force, potency. 5.   zeal, push.