difference between being under the weather and being ill

[chance22]

I wonder about the differences between "under the weather" and "ill". When people say "You look under the weather", can I simply use "You look ill" or "You look sick" to express the same idea?

 

[abaka]

To look ill is more serious than to look under the weather. The common cold rarely makes one look really ill.

 

[chance22]

To look ill is more serious than to look under the weather. The common cold rarely makes one look really ill.

Thank you so much. So that means that in the following multiple choice exercise,
A: What’s the matter? You look _______.
B: Yeah, I know. I’m just getting over the flu.
I have to choose "under the weather" instead of "ill" or "sick"?

 

[abaka]

I would choose "under the weather". The sick person is getting over the flu and is already up and about.

 

[emsr2d2]

Generally, it's not polite to say to someone "You look ill". It's possible they're just very tired or stressed so they might not appreciate being told they look ill. Mind you, that's in BrE where we tend to be quite polite! You might say "Are you OK? You look a bit peaky?" or "Are you OK? You look a bit under the weather today" but with the exception of my family members and very close friends, I've never told anyone they actually look ill.

In your dialogue example, "What's the matter?" could also come across as rather abrupt and potentially impolite. Using "Are you OK?" is safer.

Again, in other variants of English, the more "straight down the line" approach might be perfectly acceptable.