“Fulfill” and “fulfil” are regional base-form spellings of the same verb. Cambridge identifies fulfill as US and fulfil as mainly UK, while also showing doubled-l inflected forms such as fulfilled.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
Use “fulfill” in US English and “fulfil” in UK-oriented English; inflected forms such as “fulfilled” still double the final l.
Key details
Confusion Familyregional-spelling
Noun Variant ScopeCambridge identifies fulfill as the US spelling and fulfil as mainly UK; inflected forms still use doubled l in fulfilled/fulfilling.
Rule Familyregional-orthography
Termsfulfill, fulfil
Further guidance
Core difference
“Fulfill” is the standard US spelling and “fulfil” is mainly UK for the same verb.
Fast Test
Use the base spelling required by the intended variety and keep that convention consistent.
Variant Boundary
The distinction concerns the base spelling; the cited fulfil entry also shows “fulfilled” and “fulfilling,” so do not infer a one-l rule for every inflected form.
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.
“Aging” and “ageing” are established regional spellings. Cambridge labels aging as US and ageing as UK, so the choice should follow the intended variety or house style.
“Analyze” is the standard US spelling and “analyse” is the standard UK spelling of the same verb. The distinction is regional spelling; use the form that matches the target variety or editorial style.
“Behavior” is the US spelling and “behaviour” is the UK spelling. Use the form consistent with the regional variety or editorial style of the document.
Both “canceled” and “cancelled” are standard past-tense spellings of “cancel”; US English usually uses one l, while UK English normally uses two. Cambridge records the -ll- forms and notes that US English usually uses -l-, so the difference should be presented as a regional preference rather than a correctness split.
