✔ 最佳答案
In the medical sense, they mean almost the same thing, and in most cases they may be used interchangeably. Ill might be slightly more formal.
There is a grammatical difference, If you are sick and get worse, you can be sicker. Ill does not have a comparative form in the same pattern. "iller" is not standard English. If someone is ill and gets worse, you just have to say, "He has gotten worse."
In other uses, the difference does not follow any pattern.
You would say, "An ill wind," meaning it brought some misfortune. A "sick wind" doesn't have any meaning.
Likewise, if you don't like something, you might say, "That s sick." Il"l won t do here.
English does not have consistent rules for things like this. Each expression must be learned.