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。
1 關系代詞引導的定語從句
關系代詞有：who, whom, whose, that, which等。
關系副詞有：when, where, why等。
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）
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. 農村出現了前所未有的繁榮。（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）
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. 農村出現了前所未有的繁榮。（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）
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"結構，因此常常和"介詞+ which"結構交替使用，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。
3 判斷關系代詞與關系副詞
方法一： 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聯系在一起。此兩題錯在關系詞的誤用上。
方法二： 準確判斷先行詞在定語從句中的成分(主、謂、賓、定、狀)，也能正確選擇出關系代詞/關系副詞。
例1. Is this museum ___ you visited a few days age?
A. where B. that C. on which D. the one
例2. Is this the museum ____ the exhibition was held.
A. where B. that C. on which D. the one
答案：例1 D，例2 A
例1變為肯定句： This museum is ___ you visited a few days ago.
例2變為肯定句： This is the museum ___ the exhibition was held.
在句1中，所缺部分為賓語，而where, that, on which都不能起到賓語的作用，只有the one既做了主句的表語，又可做從句的賓語，可以省略關系代詞，所以應選D。
而句2中, 主、謂、賓俱全，從句部分為句子的狀語表地點，既可用副詞where，又因 in the museum詞組，可用介詞in + which 引導地點狀語。而此題中，介詞on 用的不對，所以選A。
關系詞的選擇依據在從句中所做的成分，先行詞在從句中做主、定、賓語時，選擇關系代詞 (who, whom, that, which, whose)； 先行詞在從句中做狀語時，應選擇關系副詞 ( where 地點狀語，when 時間狀語，why 原因狀語) 。
4 限制性和非限制性定語從句
1) 定語從句有限制性和非限制性兩種。限制性定語從句是先行詞不可缺少的部分，去掉它主句意思往往不明確；非限制性定語從句是先行詞的附加說明，去掉了也不會影響主句的意思，它與主句之間通常用逗號分開.
例如：This is the house which we bought last month. 這是我們上個月買的那幢房子。（限制性）
The house, which we bought last month, is very nice.這幢房子很漂亮，是我們上個月買的。（非限制性）
The house, which we bought last month, is very nice.這幢房子很漂亮，是我們上個月買的。（非限制性）
2) 當先行詞是專有名詞或物主代詞和指示代詞所修飾時，其后的定語從句通常是非限制性的.
例如：Charles Smith, who was my former teacher, retired last year. 查理·史密斯去年退休了，他曾經是我的老師。
My house, which I bought last year, has got a lovely garden. 我去年買的的那幢房子帶著個漂亮的花園。
This novel, which I have read three times, is very touching. 這本小說很動人，我已經讀了三遍。
3) 非限制性定語從句還能將整個主句作為先行詞, 對其進行修飾, 這時從句謂語動詞要用第三人稱單數.
My house, which I bought last year, has got a lovely garden. 我去年買的的那幢房子帶著個漂亮的花園。
This novel, which I have read three times, is very touching. 這本小說很動人，我已經讀了三遍。
3) 非限制性定語從句還能將整個主句作為先行詞, 對其進行修飾, 這時從句謂語動詞要用第三人稱單數.
例如：He seems not to have grasped what I meant, which greatly upsets me. 他似乎沒抓住我的意思，這使我心煩。
Liquid water changes to vapor, which is called evaporation. 液態水變為蒸汽，這就叫做蒸發。
說明：關系代詞that和關系副詞why不能引導非限制性定語從句。
Liquid water changes to vapor, which is called evaporation. 液態水變為蒸汽，這就叫做蒸發。
說明：關系代詞that和關系副詞why不能引導非限制性定語從句。
