which的用法
1.(用作疑問代詞)哪一個,哪一些
Which is my seat?
哪個座位是我的?
2.(用做關系代詞)那一個,那一些
He also had a gun with which to defend himself.
他還有一把自衛用的槍。
He invited us to dinner, which was very kind of him.
他邀請我們吃晚飯,他這么做真是太客氣了。
She was very fond of speaking French, which indeed she spoke well.
她很喜歡講法語,而且確實講得不錯。
He lives in the house which is opposite ours.
他住在我們對面的那棟房子里。
which作為形容詞用法如下
1.(用作疑問形容詞)哪一個,哪一些
Which university did you go to, Oxford or Cambridge?
你上過哪所大學?牛津還是劍橋?
2.(用作關系形容詞)這個,這些
The doctor told him to give up smoking, which advice he took.
醫生叮囑他戒煙,他接受了這一忠告。
其他用法
1、在后置的非限制性定語從句中代替上文出現的事物或情況（單數或復數）。
2、在問句中作為疑問代詞，在名詞從句中作為連接代詞用，其含義為“哪個、哪些”。
3、如果非限制性定語從句的先行詞不是指主句內容，而是指具體的人、時間、地點，則不用which。