定語從句（Attributive Clauses）在句中做定語,修飾一個名詞或代詞,被修飾的名詞,詞組或代詞即先行詞.定語從句通常出現(xiàn)在先行詞之后,由關系詞（關系代詞或關系副詞）引出.
關系代詞有：who,whom,whose,that,which等.
關系副詞有：when,where,why等.18.1 關系代詞引導的定語從句
關系代詞所代替的先行詞是人或物的名詞或代詞,并在句中充當主語、賓語、定語等成分.關系代詞在定語從句中作主語時,從句謂語動詞的人稱和數(shù)要和先行詞保持一致.
1）who,whom,that
這些詞代替的先行詞是人的名詞或代詞,在從句中所起作用如下：
Is he the man who/that wants to see you?
他就是你想見的人嗎?（who/that在從句中作主語）
He is the man whom/ that I saw yesterday.
他就是我昨天見的那個人.（whom/that在從句中作賓語）
2) Whose 用來指人或物,(只用作定語,若指物,它還可以同of which互換）,例如：
They rushed over to help the man whose car had broken down.那人車壞了,大家都跑過去幫忙.
Please pass me the book whose (of which) cover is green.請遞給我那本綠皮的書.
3）which,that
它們所代替的先行詞是事物的名詞或代詞,在從句中可作主語、賓語等,例如：
A prosperity which / that had never been seen before appears in the countryside.農(nóng)村出現(xiàn)了前所未有的繁榮.（which / that在句中作賓語）
The package (which / that) you are carrying is about to come unwrapped.你拿的包快散了.(which / that在句中作賓語 18.2 關系副詞引導的定語從句
關系副詞可代替的先行詞是時間、地點或理由的名詞,在從句中作狀語.
1）when,where,why
關系副詞when,where,why的含義相當于"介詞+ which"結(jié)構(gòu),因此常常和"介詞+ which"結(jié)構(gòu)交替使用,例如：
There are occasions when (on which) one must yield.任何人都有不得不屈服的時候.
Beijing is the place where (in which) I was born.北京是我的出生地.
Is this the reason why (for which) he refused our offer?這就是他拒絕我們幫助他的理由嗎?
2）that代替關系副詞
that可以用于表示時間、地點、方式、理由的名詞后取代when,where,why和"介詞+ which"引導的定語從句,在口語中that常被省略,例如：
His father died the year (that / when / in which) he was born.他父親在他出生那年逝世了.
He is unlikely to find the place (that / where / in which) he lived forty years ago.他不大可能找到他四十年前居住過的地方.
用關系代詞,還是關系副詞完全取決于從句中的謂語動詞.及物動詞后面無賓語,就必須要求用關系代詞；而不及物動詞則要求用關系副詞.例如：
This is the mountain village where I stayed last year.
I'll never forget the days when I worked together with you.
判斷改錯（注：先顯示題,再顯示答案,橫線；用不同的顏色表示出.）
（錯） This is the mountain village where I visited last year.
（錯） I will never forget the days when I spent in the countryside.
（對） This is the mountain village (which) I visited last year.
（對） I'll never forget the days (which) I spent in the countryside.
習慣上總把表地點或時間的名詞與關系副詞 where,when聯(lián)系在一起.此兩題錯在關系詞的誤用上.