Vigor and vigour mean exactly the same thing: strength, energy, and force, whether that is physical stamina or the intensity behind an argument. Vigor is the American spelling and vigour is the British one. Picture someone attacking a garden with surprising vigor (US) or tackling a hike with real vigour (UK); either way, the energy is identical.
The core difference
Vigor and vigour both mean physical or mental strength and energy; the spelling simply follows American versus British convention.
- vigor — American spelling for strength, energy or force: She attacked the garden with surprising vigor.
- vigour — British spelling of the same word: Despite his age, he tackled the hike with real vigour.
How to tell them apart
Both spellings cover the same ground: physical strength and good health, the intensity or determination behind how something is said or done, and even, in biology, the healthy growth of a plant or organism. Both trace back to the Latin vigor, from vigere, meaning to be lively or flourish, a root shared with vigorous and vigil.
Writers usually slip between the two when moving between American and British sources, since vigor/vigour follows the same -or/-our pattern as color/colour and honor/honour. Choose one spelling and keep it consistent across a document.
