/wɪtʃ; US hwɪtʃ ||; hwɪtʃ/det pronoun1 used in questions to ask sb to be exact, when there are a number of people or things to choose from （用于涉及多个选择的疑问句，以获得确切信息）: Which hand do you write with? 你用哪只手写字？Which is your bag? 哪一个包是你的？She asked me which book I preferred. 她问我喜欢看哪本书。I can't remember which of the boys is the older. 我记不得哪一个男孩的年纪较大。
Which or what ? We use which when there is only a limited group or number to choose from Which car is yours? The Ford or the Volvo (= there are only two cars there)? We use what when the group is not limited What car would you choose (= of all the makes of the car that exist), if you could have any one you wanted? What is your name? 用which还是what？选择有限时宜用which：Which car is yours? The Ford or the Volvo?哪一辆是你的车？“福特”还是“富豪”牌的？如果选择是无限的就用what：What car would you choose, if you could have any one you wanted?如果你可以得到一辆汽车，你选哪一种？·What is your name?你叫什么名字？ 2 used for saying exactly what thing or things you are talking about （用于确切地指明某事物）: Cars which use unleaded petrol are more eco-friendly. 使用无铅汽油的汽车更有利于保护生态环境。 (formal 正式) The situation in which he found himself was very difficult. 他发觉自己已身陷困境。 ☞In less formal English we would write The situation which he found himself in was very difficult.In the final example, ‘which’ is often left out The situation he found himself in... 比较非正式的写法可作：The situation which he found himself in was very difficult.最后一个例句中的which通常可省去：The situation he found himself in...
3 used for giving more information about a thing or animal （用于作补充）: My first car, which I bought as a student, was a Renault. 我的第一辆车是雷诺牌的，那是学生时代买的。 ☞There is a comma before ‘which’ and at the end of the part of the sentence that it introduces. 在which之前及which所引导的从句的末尾都得加上逗号。
4 used for making a comment on what has just been said （用于对刚说的话下评语）: We had to wait 16 hours for our plane, which was really annoying. 我们得等16个小时才搭上我们的那班飞机，真令人讨厌。 ☞There is a comma before ‘which’. which之前要用逗号。