U

vigor

noun

active strength or force.
healthy physical or mental energy or power; vitality.
energetic activity; energy; intensity: The economic recovery has given the country a new vigor.
force of healthy growth in any living matter or organism, as a plant.
active or effective force, especially legal validity.

c.1300, from Anglo-French vigour, Old French vigor, from Latin vigorem (nominative vigor) “liveliness, activity, force,” from vigere “be lively, flourish, thrive,” from PIE *wog-/*weg- “be lively or active” (see vigil).

see vim and vigor.