Fiber vs. Fibre
“Fiber” and “fibre” are regional spellings of the same noun. Cambridge labels fiber the US spelling and fibre the UK form.
Use “fiber” in US English and “fibre” in UK English unless a required house style says otherwise.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| American English spelling | fiber | Use “fiber” in US-oriented copy. |
| British English spelling | fibre | Use “fibre” in UK-oriented copy. |
| fixed names or quotations | preserve the established spelling | Do not normalize a quoted or official form merely to match house style. |
Quick tests
Meaning / construction test
Is the document following a defined US or UK spelling convention?
If yes: Use the spelling required by that convention and keep it consistent.
If no: If no regional house style is specified, choose one variety and apply it consistently.
Caveat: The two spellings represent the same noun; the choice is regional or editorial rather than a difference in meaning.
Examples
The label lists dietary fiber.
“Fiber” follows American spelling.
The label lists dietary fibre.
“Fibre” follows British spelling.
Keep the published spelling inside a direct quotation.
Quoted wording may preserve its source variety.
Further guidance
Core difference
Cambridge identifies “fiber” as the US spelling of “fibre,” while the “fibre” entry is marked UK.
Fast Test
Match the spelling to the regional or house style required by the document, then keep that choice consistent.
Variant Boundary
The spelling changes by regional convention; the core noun meanings remain aligned.
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.
- Fiber — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Fiber identified as the US spelling of fibre
- Fibre — Cambridge Dictionary (opens in a new tab)Cambridge Dictionary · Fibre identified as the UK form corresponding to US fiber