The word sick and ill are similar in meaning: feeling or being unwell, but they have clear differences in usage. We can say “I’m going to be sick” to mean I’m going to vomit, but not “
I’m going to be ill.“ We can say “I’m sick of you!” to mean I’m very angry with you, but you can’t say “ I’m ill of you!“ Here are some expressions that can only be used with sick:
As sick as a dog
Meaning: to be very ill; to vomit a lot
– She’s as sick as a dog from that long trip. I don’t think she will come to the office today.
As sick as a parrot
Meaning: to be very disappointed
– Graham was sick as a parrot when he heard Manchester had lost the match.
Be worried sick
Meaning: to be very worried
– It’s almost midnight, but Julie hasn’t come home yet. I’m worried sick about her.
Sick to one’s stomach
Meaning: feeling of nausea
– She was sick to her stomach after knowing that her husband had lost all his money on gambling.
Sick to death of something
Meaning: to extremely bored of something
– I’m sick to death of the constant talk about the workers strike.
Sick and tired of something
Meaning: be very angry and bored of unpleasant thing that has been happening for too long
– You’ve been giving me the same old excuses for months and I’m sick and tired of hearing them!
Call in sick
Meaning: to call the office/school to tell that someone is sick and can’t come in
– Four of our office staff called in sick today.
Meaning: a joke intended to be humorous, but actually in a very bad taste
– He always tell sick jokes about the Chinese people.