當關系副詞引導的定語從句換為關系代詞引導時，用“介詞+which”引導定語從句或者which作從句的謂語動詞的賓語且從句的謂語動詞是不及物動詞時，關系代詞which前要加介詞。

例句：

1.I will never forget the days when we worked together.

我永遠忘不了我們在一起工作的日子。

關系副詞when引導定語從句，換為關系代詞which引導，關系代詞前要加介詞，即“介詞+which”

I will never forget the days in which we worked together.

這種情況下關系代詞前加介詞。

2.The film which they are talking about was shown a month ago.

他他們在在談論的電影一個月前放過。

句子中的是介詞，也可以放在關系代詞前。

The film about which they are talking was shown a month ago.

當先行詞作定語從句的邏輯賓語且從句的謂語動詞是不及物動詞時，從句的謂語動詞後面必須加適當的介詞，介詞也可以放在關系代詞which的前面，這樣就出現了“介詞+關系代詞which”.

的形式。

關系副詞引導的定語從句也可以轉換成“介詞+關系代詞which”.

例句：

1.This is the house which he lives in.

可以轉換成：

This is the house in which he lives.

2.This is the reason why he was late for class.

可以轉換成：

This is the reason for which he was late for class.

"介詞+關系代詞"引導的定語從句關系代詞whom,which在定語從句中作介詞的賓語時,可以跟介詞一起放在主句和從句之間;

常用的有
why=for which
where=in/ at/ on/ ... which (介詞同先行詞搭配)
when=during/ on/ in/ ... which (介詞同先行詞搭配)

①名詞+of+which（=of which+名詞=whose+名詞）通常放在先行詞的後面。

I’d like a room the window of which looks out over the sea.

I’d like a room of which the window looks out over the sea.

I’d like a room whose window looks out over the sea.

我要一間窗戶面臨大海的房間。

②介詞+which的替代作用

（1）作時間狀語替代when

There used to be a time at whichduring which（=when）the Chinese people struggled for freedom.

華人曾有一段為自由而鬥爭的日子。

（2）作地點狀語替代where

This is the office in which（=where）I used to work.

這是我過去工作過的辦公室。

（3）作原因狀語替代why

I’d like you to explain the reason for which（=why）you were absent.

我想讓你解釋一下缺席的原因。

（4）作方式狀語替代that或省略

There are many ways in which（=that省略）we can solve the problem.

解決這個問題有很多方法。

當定語從句中的which是做介詞的賓語，就要在which前加介詞。舉個例子，This is the city which I lived in.或 This is the city in which I lived.在這個從句中，which就是做介詞in 的賓語，所以前面一定有in。你可能覺得別扭，幹嘛有in 啊？直接把which放在live後不就行了嗎？ 這時你可能就沒有了解一個概念 live 這個動詞是不及物動詞，它後面沒有賓語。不能接名詞。但是可以接介詞短語，來做這個動詞的狀語（一般來說是地點狀語），也就是說不及物動詞後不接名詞但是能夠接介詞短語才能和名詞相見。這是個搭配模式：不及物動詞+介詞短語。

引用別人的，希望對你有幫助