which是英语关系代词，在英语学习和交流中which的用法很常见，下面淘教中国网详细介绍一下关于which的用法：

　　1. 英语中which既可引导限制性定语从句，也可用作非限制性定语从句。如：

　　This is the photo (that) I took. 这就是我拍的照片。

　　The river, which flows through London, is called the Thames. 这条流经伦敦的河叫泰晤士河。

　　2. which引导定语从句时，它在从句中主要用作主语或宾语，但有时也可用作定语，在意义上大致相当于this或that。如：

　　We told him to consult the doctor, which advice he took. 我们叫他去看医生，他听取了我们的劝告。

　　He is studying economics, which knowledge is very important today. 他学经济学，这种知识现今很重要。

　　注意，它与用作定语的关系代词whose用法不同——whose引导定语从句时，它在意义上大致相当于one’s。如：

　　Wolves are highly social animals whose success depends upon cooperation. 狼是高度群体化的动物，它们的成功依赖于合作。

　　3. 英语中which原则上只指物，不指人；指人要用who。但是，有时指的不是具体的某人，而是指人的属性（如职业、身份、地位、职务、品质、特征等），则要用which 而不用who。如：

　　He talked like a scholar, which he was not. 他说起话来像个学者，其实他没什么学问。

　　She talked like a native, which she hardly was. 她说起话来像是个本地人，其实她不见得是。

　　They accused him of being a traitor, which he was. 他们指控他是叛徒，他真是叛徒。

　　4. 注意不要一看到句前有逗号，就以为一定要用which来引导非限制性定语从句。如以下几句逗号后的that均不能换成which（原因是逗号前的句子为状语从句）：

　　If a book is in English, that means slow progress for you. 如果一本书是用英语写的，那就意味着你要读慢些。

　　If he’s only interested in your looks, that just shows how shallow he is. 如果他只对你的相貌感兴趣，那就说明他相当浅薄。

　　When I say two hours, that includes time for eating. 我说两小时，那是包括了吃饭的时间。

　　5. 比较下面两句，第一句用了连词but，其后用them；第二句没用连词but，其后用which：

　　She wrote a lot of novels, but none of them were popular.=She wrote a lot of novels, none of which were popular. 她写过许多本小说，但没有一本是受欢迎的。

　　6. 有时可以见到“介词+关系代词+不定式”这样的结构（可视为一种紧缩的定语从句）。比较：

　　She must have time in which to grow calm.=She must have time in which she can grow calm. 她必须有冷静下来时的时间。

　　She had some money in the bank, with which to help her mother.=She had some money in the bank, with which she could help her mother. 她银行里有些钱用来帮助她的母亲。

　　值得指出的是，这类结构中的介词不能没有，并且该介词也不能位于不定式后面，比较：

　　There the children had a garden in which to play.（很正式）

　　There the children had a garden in which they could play.（较正式）

　　There the children had a garden to play in.（较口语化）在那儿孩子们有个可以玩耍的花园。

　　但是不能说：There the children had a garden which to play in.

　　7. 有时可见到由which引导的非限制性定语从句单独成句。如：

　　Mary is enormously respected. Which is not to say you are not an exceptionally able lady. 玛丽非常受尊重，但这并是说你不是一位极为能干的女士。