Spelling: UK vs US

A comprehensive* list of British and American spelling differences.

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It would be impractical to try to offer a truly comprehensive list of any words like this, since you can make a couple of different verb forms out of almost any noun, a couple of different nouns out of nearly any verb, etc. So capital can become capitalize and capitalizes, then capitalization and capitalizing, then capitalizations and capitalizings, and even capitalizationing and capitalizationings. And then you can negate or reverse them: decapitalizationing, recapitalizationing, pseudocapitalizationing, etc. This is why any estimates of total number of words in the language or someone's vocabulary are fairly meaningless.

For more details, check this Wikipedia.