ill表示“生病的、有病的”这一意思时，一般用作表语，不能作定语；而sick既可以作表语又可以作定语，如“病人”可以说a sick man 或the sick，但不能说an ill man 或the ill.又如：She is ill/sick in bed.她卧病在床。She is looking after her sick father.她在照顾她生病的父亲。
sick例句
1. I get sick of being thought of as a political automaton.
我讨厌被看作政治机器。
2. When we are off sick, we only receive half pay.
我们请病假的时候只能拿一半薪水。
3. He was worried sick about what our mothers would say.
对于我们双方的母亲会说什么他十分担心。
4. I really don't feel a bit sick, no night sweats, no fevers.
我真的感觉一点毛病也没有，没盗汗也不发热。
5. There are no paid holidays or sick leave if you are self-employed.
如果你是个体户，就没有带薪休假或病假。
ill例句
1、He was ill, but made out to be all right.
他病了，但却装着没有病的样子。
2、These nouns refer to the feeling or expression of deep-seated ill will.
这些名词指根深蒂固的恶意的感情或表述。
3、The new arrangement caused a lot of ill feeling.
新的安排引起了许多人的不满。
4、You should not speak ill of your friend.
你不应该说你朋友的坏话。
5、Jim accepted that he was wrong with an ill grace.
吉姆十分勉强地承认自己错了。