The Columbia Guide to Standard American English
These words are interchangeable and Standard in American English. In Britain, sick means “nauseated” or “vomiting, throwing up,” whereas ill is the general word for “feeling unwell.” Hence seasick has as its second part the British sense of sick. Like American English vomit, British sick can also be a noun meaning “the regurgitated matter itself.” There are possibly some occasional class nuances too: an American seeking to sound refined may more often use ill than sick, just as an illness may be thought by some to be a more elegant thing to have than a sickness.

Dear Teacher,Emotion: smile

As an Canadian, do you use sick as an American or an Englishmen?

I'm very grateful for the precious help your are giving.

Hello again,

Here are some comments from a Canadian perspective. If I don't feel well, I'd say I am or feel sick, particularly in speaking rather than writing. If I feel nauseated, I'd say something like I feel sick or I feel nauseated.

However, if I were diagnosed with a serious disease, I'd be more inclined to say 'I am ill'. It sounds more serious and more longterm.

I hope this helps. Clive
I don't recognize the distinction the guide makes about BrE usage. Over here, you phone in sick, you're off sick, you take sick leave – all while you're ill.

And if you're ill, you could be throwing up – or being sick.

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Sick or ill Emotion: ick! Emotion: crying
 MrPedantic's reply was promoted to an answer.
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