I had to come alone, for Clara has been very ill and could not travel.

我不得不一个人来，因为克拉拉病得很重，不能旅行。

youdao

I'm ill, so I can't come in.

我病了，所以不能参加了。

youdao

He didn't come today; perhaps he's ill.

他今天没来，许是生病了。

《新英汉大辞典》

But even the ill-informed can come up with a good idea which is what I think they have done.

FORBES: Links 10 Nov: Finally, An Occupy Wall Street Idea We Can All Get Behind, The Rolling Jubilee

Samsung's ill-fated car business, which has come to represent the chaebol's resistance to reform, was the test of Mr Kim's resolve.

ECONOMIST: South Korean restructuring

Actually, the suspicion that American firms have stitched up the lucrative contracts to come in Iraq is probably ill-founded.

ECONOMIST: The reconstruction business