“Meter” and “metre” overlap only partly. Cambridge marks metre as the UK spelling of the metric length unit and meter as the US unit form, while “meter” also has separate device senses such as electricity meter.
ReviewedEvidence2 sourcesSectionEnglish Usage
Quick answer
For the metric length unit, use “meter” in US English and “metre” in UK English; a measuring device is “meter,” including in British English.
Key details
Confusion Familyregional-spelling
Rule Familyregional-orthography
Termsmeter, metre
Variant ScopeRegional variation applies to the metric-length sense; meter also has non-regional device senses.
Further guidance
Core difference
For the unit of length, Cambridge gives UK “metre” and US “meter”; for a measuring device, the dictionary uses “meter.”
Fast Test
Match the spelling to the regional or house style required by the document, then keep that choice consistent.
Variant Boundary
Do not mechanically replace every “meter” with “metre” in British text, because device senses remain “meter.”
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.
