While and whilst are both acceptable. I prefer while because it is simpler and less formal than whilst.
Michael Quinion, World Wide Words, says:
‘In both cases [while/whilst and among/amongst], the form ending in -st actually contains the -s of the genitive ending (which we still have today, though usually written as ’s, of course). In Middle English, this was often added to words used as adverbs (as while became whiles, which often turned up in the compound adverbs somewhiles and otherwhiles). What seems to have happened is that a -t was later added in the south of England through confusion with the superlative ending -st (as in gentlest).
‘Both while and whilst are ancient, though while is older. There’s no difference in meaning between them. For reasons that aren’t clear, whilst has survived in British English but has died out in the US. However, in Britain it is considered to be a more formal and literary word than its counterpart. I have a small weakness for it, for which I’ve been gently teased in the past.’
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