■in case 与in case of性质不同
in case 可用作连词和副词，而in case of 用作介词。如：
In case of fire, ring the bell. 如发生火灾，请按铃。
The wall was built along the river in case of floods. 沿江筑了堤坝以防有洪水。
有时两者可以互相转换。如：
In case I’m not here, ask my brother to help you.=In case of my not being here, ask my brother to help you. 如果我不在，可让我弟弟帮助你。
■in case与if有时意思不同
注意下面两个句子在意思上的不同：
I’ll come tomorrow in case Ann wants me. 明天我要来，以备安找我。
I’ll come tomorrow if Ann wants me. 如果安找我，我明天就来。
但是，介词短语 in case of…与 if there is…的意思却相同。如：
In case of accident phone 999.=If there is an accident phone 999. 如果发生事故，请拨电话999。
