Energy

Internal or inherent power; capacity of acting, operating, or producing an effect, whether exerted or not; as, men possessing energies may suffer them to lie inactive.

Power efficiently and forcibly exerted; vigorous or effectual operation; as, the energy of a magistrate.

Strength of expression; force of utterance; power to impress the mind and arouse the feelings; life; spirit; -- said of speech, language, words, style; as, a style full of energy.

Capacity for performing work.

The capacity to do work

The capacity to do work or produce heat in an organism

(physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs; "energy can take a wide variety of forms"

a healthy capacity for vigorous activity; "jogging works off my excess energy"; "he seemed full of vim and vigor"

an imaginative lively style (especially style of writing); "his writing conveys great energy"; "a remarkable muscularity of style"