The difference between while and whilst
TLDR: Interchangeable when you mean ‘at the same time as’ or ‘during the time that’.
The word while has many functions in a sentence. It can be a conjunction, a noun, a verb and even a relative adverb.
while (conjunction)—at the same time as, during the time that; whereas; although
Nothing was read in the book club while she was on holiday.
He was happy to sit and talk, while she wanted to go for a run.
While I wouldn’t recommend it, it might be your only option.
while (noun)—an unspecified length of time
She went to the shops a little while ago.
‘Can I stay here a while?’ she asked anxiously.
while (verb)—to pass time at one’s leisure
‘We need something to do to while away the hours until dinner.’
while (relative adverb)—during which
The period while my father’s snores are the quietest is the only time I get my sleep.
It is widely debated by English users whether whilst is simply the outdated, more old-fashioned version of while or whether it has its own rules of usage. While these two words can be used interchangeably and without incident, you should keep in mind that there is a certain impression that is derived from using whilst. Literary uses aside, you may come across as a bit pompous if you use whilst in a modern context, such as business emails or everyday conversation.
There does not appear to be a geographical element to distinguish between those who use it and those who do not as both the British and American versions of English are slowly phasing out whilst in preference to while.
I personally do not use whilst as I find while covers all my literary, conversational and professional needs and feels a little more accessible to all English speakers. However, if you do wish to use whilst, then it can be used interchangeably with while when you mean ‘at the same time as’ or ‘during the time that’. For example:
The dishes went unwashed whilst my parents were out.
I waited patiently whilst the teacher berated her students.
Finally, though it is a shame that some words become less used before they gradually disappear, it is important to note that English is an ever-changing language and always has been. It has had many influences already (such as Latin, Greek, French, German, Old Norse, Spanish, Dutch and Arabic) and the rise of its use across the globe will only increase the number of influences. New words will be introduced, old words will fall by the wayside and native speakers will strip away unnecessary formality as yet more and more cultures adopt English.
Now I need a tissue. The demise of whilst has brought a tear to my eye.