1. 由“介詞+關(guān)系代詞”引導(dǎo)的定語(yǔ)從句主要用于正式文體，在非正式文體中通常將介詞放至句末。如：This is the man to whom I referred. 我指的就是這個(gè)人。This is the man (whom) I referred to. 我指的就是這個(gè)人。

2. 直接用于介詞后作賓語(yǔ)的關(guān)系代詞which不能換成that，直接用于介詞后作賓語(yǔ)的關(guān)系代詞whom不能換成who。但若介詞用于句末，則用作賓語(yǔ)的which, whom也可換成that, who，或者省略不同。如：這是一個(gè)我們討論了許多的問(wèn)題。This is a subject about which we have talked a lot.(which不能換成that，也不能省略)This is a subject which we have talked about a lot. 這是一個(gè)我們討論了許多的問(wèn)題。(which可以換成that，也可以省略)?

3. 關(guān)系副詞when, where, why根據(jù)情況有時(shí)可換成“介詞+關(guān)系代詞which”。如： That is the day when [=on which] he was born. 那就是他出生的日子。That is the house where [=in which] he lived. 那就是他住過(guò)的房子。That is the reason why [=for which] he must apologize. 那就是他必須道歉的原因。

4. 在很正式的文體中，“介詞+關(guān)系代詞”引導(dǎo)的定語(yǔ)從句可緊縮成“介詞+關(guān)系代詞+不定式”結(jié)構(gòu)。如：在那兒孩子們有個(gè)玩耍的花園。正：There the children had a garden in which to play. (很正式)正：There the children had a garden in which they could play. (較正式)正：There the children had a garden to play in. (較口語(yǔ)化)注：這類“介詞+關(guān)系代詞++不定式”結(jié)構(gòu)中的介詞不能沒(méi)有，也不能放在句末。如不能說(shuō)There the children had a garden which to play in.