Simone
区别在于：1、be ill是延续性状态，可以跟since短语，而fall ill是瞬间性动词，不可以延续，因此不可以和since短语连用。2、这两个词语都有生病的意思，be ill表示生病的状态，而fall ill强调生病的过程。相似的短语还有feel ill，意思是感觉生病了，不舒服，主要强调自我感觉，但是不一定真的生病了。
fall ill造句：
If you don not eat on time and go to bed on time，you will fall ill。如果再不按时吃饭，按时睡觉，你就会病倒的。
She has not had a rest for days，and I am afraid she'll fall ill。她已经好几天没休息了，我担心她会病倒。
The grandmother next door suddenly fell ill and soon passed away。隔壁奶奶突然病倒了，不久就去世了。
be ill造句：
She has been ill since she came home from the rain at the seaside yesterday。自从昨天在海边淋雨之后，回家她就生病了。
She does not want to eat anything because she has been ill for a while。因为她这段时间生病了，所以什么东西都不想吃。
Since his illness he has been unable to do anything but lie in bed。自从他生病之后很多事情都做不了，只能在床上躺着。
