Vigor

Part of speech: noun (n.)

1. Active strength or force of body or mind; capacity for exertion, physically, intellectually, or morally; force; energy. The vigor of this arm was never vain. Dryden.

2. Strength or force in animal or force in animal or vegetable nature or action; as, a plant grows with vigor.

3. Strength; efficacy; potency. But in the fruithful earth . . . His beams, unactive else, their vigor find. Milton.

Part of speech: verb (v.)

To invigorate. [Obs.] Feltham.