fall ill

fall ill
患病，病倒
She has to stay home because her son fall ill.
因为儿子生病所以她得待在家里。
He had the misfortune to fall ill on the day of the examination.
他很倒霉，在考试当天生病了。
Be careful not to fall ill．
注意不要生病了。
She's afraid her husband will fall ill.
就可得知她担心的是丈夫的健康。
It is easy for the old to fall ill in winter.
老年人很容易在冬天生病。

详解：

fall ill 是瞬间性动词。be ill 是延续性状态。比如：
I has been ill for 3 days.(我生病三天了)，这里强调这种状态已经延续3天了，这是就不能用fall ill了。
Mary _____ ill since she left her hometown last winter。
A. fell B. has fallen C. was D. has been
答案为D。fall ill 是瞬间性动词，不可以延续，所以不能和since 短语连用。
be ill 是延续性状态，所以可以跟since短语。

fall asleep<-->far away