which意思及用法：
adj.哪一个;哪一些
pron.哪一个;哪些
which的用法总结：
1、在后置的非限制性定语从句中代替上文出现的事物或情况(单数或复数)。
2、在问句中作为疑问代词，在名词从句中作为连接代词用，其含义为“哪个、哪些”。
3、如果非限制性定语从句的先行词不是指主句内容，而是指具体的人、时间、地点，则不用which。
一、关系代词that 和which 在定语从句中作主语和宾语，放在先行词和定语从句之间，起联系作用。指物时，一般情况下可互换。如： Here is the pen that/which you lost yesterday.(that/which 指物作宾语) A plane is a machine that/which can fly.(that/which 指物，作主语) He is the most careful boy that I know.(that 指人,作宾语) The man that works in this room is a chemist.(that 指人,作主语)
二、that,which 在从句中作主语时，不能省略。作宾语时在口语中和非正式问题中经常省略。如上例1 和中的that,which 都可省略。
三、关系代词在主语从句中作主语时，从句的谓语动词的人称和数须和先行词一致。 Wheat is a plant that/which is grown in the north of China.
四、在定语从句中，关系代词that 和which 指物时，一般没有区别，但下列几种情况中不能互换：
只能用that 的情况：
a)先行词为 all,everything,nothing,anything,little 等不定代词时(something 后也可用which)： Is there anything (that) I can do for you in town? That’s all (that) I know.
b) 先行词被序数词所修饰时： The first thing (that) we should do is to work out a plan.
c) 先行词被形容词最高级所修饰时： This is one of the most exciting football games (that) I have ever seen. The nanjing yangtse river bridge is the longest bridge (that) they have ever seen.
d) 先行词 被only,very,no,any,same,little,one of 等词所修饰时： This is the only thing (that) we can do now. He gave me the same pen (that) he borrowed from me. Do you have any books that were written by Lu Xun? This is the very book (that) I want to read.
e) 当先行词中既有人又有物时： The man and the car (that) you want to see are all here. 你相见的人和车都在这里。
f) that 可指人，which 则不能： Who is the man that is reading the newspaper over there?
g) 在 “the time when”等结构和某些时间状语中，when 常被that 代替，而且that 往往省略： I may leave here any time I want to. During the time I was there I visited him twice.
h)way 后面可跟由that 引导的定语从句，但that 一般都省略： That was the way she looked after us.
在下列情况中，只能用which:
a) 放在介词后面做介词宾语时： This is the question about which we’ve had so much discussion. 但是，如把介词放在从句的后部，这时which 就可换为that 并常省略。如上例可改为： This is the question (that) we’ve had so much discussion about.
b) 在非限制性定语从句，无论指物指人，都不能用that。指物时，只能用which 和其他关系代词。如： All the books there,which have beautiful pictures in them,were written by him.
