Center and centre are two spellings of the same word. The difference is geographic: center is standard in American English, centre is standard in British English (and is also used in Canadian, Australian, and most other varieties of English outside the United States).
The spelling difference
Center (American English): used in the United States for all senses of the word — physical location (the city center), a point equidistant from all edges (the center of a circle), a verb (to center an argument), and as a modifier (center stage).
Centre (British English): used for the same senses but spelled with the reversed -re ending.
The difference reflects one of the most systematic spelling divergences between American and British English: words ending in -er in American English often end in -re in British English. Other examples in the same category: theater/theatre, meter/metre, fiber/fibre, caliber/calibre, saber/sabre.
Historical background
The -re ending came into English from French, which borrowed these words from Latin. Noah Webster, in his effort to simplify and Americanize English spelling in his 1828 dictionary, standardized the -er ending as more phonetically consistent with English pronunciation patterns. The British tradition retained the French-influenced -re.
When to use which
The rule is simple: match the variety of English your document is written in.
Academic paper submitted to a British journal or institution → centre
Report written for an American company or audience → center
International context without a specified regional standard → follow whatever style guide applies, or pick one and apply it consistently
Mixing center and centre in the same document creates an impression of inconsistency and is avoidable with a simple find-and-replace check.
As a verb
Both center (AmE) and centre (BrE) function as verbs: to center/centre an argument on a key claim. The conjugated forms follow the same pattern: centered/centred, centering/centring.
Trinka’s grammar checker recognizes both American and British spelling conventions and can flag inconsistent spelling within a single document.
References
Merriam-Webster. (2023). Center. https://www.merriam–webster.com/dictionary/center
Oxford Dictionaries. (2023). Centre. https://www.oxfordlearnersdictionaries.com/definition/english/centre
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