Fervor and fervour both mean intense, passionate feeling or enthusiasm, as in singing an anthem with real fervor or fervour. Fervor is the American spelling and fervour is the British one — the u is the giveaway, just like in colour or favour.
The core difference
They mean the same thing; fervor is American English and fervour is British English.
- fervor — American spelling: The crowd sang the anthem with real fervor.
- fervour — British spelling: The team played with tremendous fervour in the final.
How to tell them apart
Both words describe the same intense, passionate feeling, whether that is religious fervor/fervour, sporting fervor/fervour, or political fervor/fervour. The Latin root fervor originally meant boiling heat, from fervere, to boil or be hot, which is a useful image for the word's sense of heated enthusiasm.
Writers most often slip between the two spellings when quoting or adapting text from a source written in the other variety of English. Stick to one spelling per document, matching whichever regional style the rest of the piece uses.
