1、 引导非限制性定语从句时。例如:
Bamboo is hollow, which makes it light.竹子是空心的,这使得他很轻。
2、 当关系词前有介词时。例如:
This is the room in which Chairman Mao once lived.这就是毛主席曾经住过的地方。
3、在一个句子中有两个定语从句,其中一个定语从句的关系代词用了that, 另一个宜用which。例如:
Let me show you the novel that I borrowed from the library which was newly open to us.
4、当关系代词后面有插入语时。例如:
Here is the English grammar which, as I have told you, will help improve your English.
这就是我跟你说过的会有助于你学好英语的那本英语语法书。
5、先行词为that时。例如:
The clock is that which can tell us the time.钟是报时的装置。