Rigor vs. Rigour
Cambridge labels “rigour” as UK and “rigor” as US for the same noun and senses. This guide treats the choice as a documented spelling convention and does not invent a meaning difference between the variants.
Use “rigor” in standard US spelling and “rigour” in standard UK spelling; the meanings are the same.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| standard American spelling | rigor | Use the spelling without “u” in US English. |
| standard British spelling | rigour | Use the spelling with “u” in UK English. |
| choose between them based on meaning | no meaning contrast in this spelling pair | Keep one regional spelling consistently unless a quoted name or house style requires otherwise. |
Quick tests
Meaning / construction test
Are you writing in a consistent regional variety?
If yes: Use “rigor” for US English and “rigour” for UK English.
If no: If your publication has a house style, follow that style; the core distinction is regional spelling, not meaning.
Caveat: This is a regional spelling distinction. It does not create a difference in core meaning.
Examples
The review was conducted with scientific rigor.
“Rigor” is the standard US spelling.
The review was conducted with scientific rigour.
“Rigour” is the standard UK spelling.
Maintain the same rigor throughout the analysis.
The US spelling keeps the same meaning as UK “rigour.”
Further guidance
Core difference
Use “rigor” in standard US spelling and “rigour” in standard UK spelling; the meanings are the same.
Style Boundary
Choose the spelling that matches the audience, region, or house style, and keep that choice consistent where both forms are accepted.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Rigour — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · UK rigour and US rigor spelling distinction