energy Definition

energy
noun energies

1. The capacity for vigorous activity; liveliness or vitality.

Thesaurus: vitality, liveliness, spirit, vigour, zeal, zest, vim, pep, strength, intensity, get-up-and-go; Antonym: inertia, lethargy, weakness.
2. Force or forcefulness.
3. physics.
The capacity to do work.

Etymology: 16c: from Greek energeia, from en in + ergon work.