Dictionary.com Word FAQs
What, in general, are the differences between British and American spelling, and why do they exist?
In the US many nouns become verbs by adding -ize (e.g., standardize). These same words usually end in -ise in Britain, despite the British dictionaries which show -ize as the main form with -ise as an alternative. One consistency is the American -yze words (analyze) are all -yse in Britain. Sometimes words in British and American English are identical in meaning but spelled differently: sulfur / sulphur, hemoglobin / haemoglobin. Most words (taken from the French) in Britain ending in -our end in -or in the US (color / colour); most words in Britain ending in -tre end in -ter in the US (center / centre). The trend in American spelling is to drop letters that are not needed in a word, such as the u in "colour." The US has a greater tendency to drop silent consonants and vowels, and move to a more phonetic spelling, especially where the old spelling was a French remnant (tyre / tire). The irregular form is generally more common in British English and the regular form is more common to American English for these verbs: burnt, burned; dreamt, dreamed; learnt, learned; smelt, smelled; spelt, spelled; spilt, spilled; spoilt, spoiled. Licence / license are both valid in the US, but in Britain the former is the noun, the latter the verb (same for practice / practice). A good dictionary will indicate both American and British spellings when there is a difference. Why do the differences exist? Well, America chose to differentiate itself from Britain from its beginnings; spelling was included in that. You can read more in H.L. Mencken's essay from The American Language (New York: Bartleby, 2000, 2nd ed). The essay itself may be found online at essay from The American Language). Noah Webster, whose Blue Back Speller (1788) sold 82 million copies within a century of its publication, was a great pioneer of US English as opposed to British English. He said that establishing a national language was as important as winning the American Revolution itself. The spelling of such terms as "theater" instead of "theatre" and "color" instead of "colour" is Webster's legacy.