(一)定語從句一般由關係代詞和關係副詞引導
1、關係代詞：who, whom, whose, which, that, as
2、關係副詞：when, where, why
關係代詞和關係副詞必須位於從句之首，主句先行詞之後，起著連線先行詞和從句的作用， 同時在從句中又充當句子成分。
e.g. She is the girl who sings best of all.(關係代詞who在從句中作主語)
The comrade with whom I came knows French.(whom在從句中作介詞with的賓語)
3、關係代詞和關係副詞的用法：1)當先行詞為人時用who 作主語，whom作賓語;2)當先行詞為物或整個句子時用which ，可作主語或賓語;3)先行詞為人、物時用that ，可作主語或賓語;4)whose用作定語，可指人或物;5)關係副詞when(指時間，在定語從句中作時間狀語，where(指地點，在定語從句中作地點狀語)，why(指原因，在定語從句中作原因狀語)。
(二)限制性定語從句與非限制性定語從句
1、限制性定語從句：從句與主句關係密切，去掉從句，主句意義不完整，甚至不合邏輯。
e.g. I was the only person in our office who was invited.(去掉定語從句，意思就不完整)
2、非限制性定語從句：從句對先行詞關係不密切，去掉定從句，意思仍然完整。形式上用逗號隔開，不能that用引導。
e.g. Tom’s father, who is over sixty, still works hard day and night.(who引導非限制性定語從句，整個句子可分成兩句來翻譯)
(三)使用定語從句時特別注意的幾個問題
1、that與which的區別。
e.g. There is nothing that can prevent him from doing it. 沒有什麼能阻止他不幹那件事。
The first place that they visited in Guilin was Elephant Trunk Hill. 在桂林他們所參觀的第一個地方是象鼻山。
This is the best film that I have ever seen. 這部電影是我看過的最好的一部。
Mr Smith is the only foreigner that he knows. 史密斯先生是他認識的唯一的外華人。
2)用which而不用 that的情況：
①引導非限制性定語從句;
②代表整個主句的意思;
e.g. He had failed in the maths exam, which made his father very angry. 他數學考試沒有及格，這使他的父親很生氣。
This is the room in which my father lived last year. 這是父親去年居住過的房子。
3)as引導定語從句時的用法
①as引導限制性定語從句通常用於the same … as, such … as結構中。
e.g. I want the same shirt as my friend’s. 我要一件跟我朋友一樣的襯衫。
Such machines as are used in our workshop are made in China. 我們車間使用的這種機器是中國製造的。
②as引導非限制性定語從句既可放在主句之前，也可放在主句之後，用來修飾整個句子。通常用下列句型：as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 等。
e.g. As I expected, he got the first place again in this mid-term examination. 正如我所預料的那樣，他在這次期中考試中又獲得了第一名。
4)as 引導非限制性定語從句時與which的區別
①當主句和從句語義一致時，用as;反之，用which來引導非限制性定語從句。
e.g. He made a long speech, as we expected.
He made a long speech, which was unexpected.
②當非限制定語從句為否定時，常用which引導。
e.g. Tom drinks a lot every day, which his wife doesn’t like at all.
2. 關係代詞在從句中作主語時，從句的謂語動詞單數還是用複數應由先行詞決定。
e.g. The man who lives downstairs speaks English fluently. 住在樓下的那個人英語說得很流利。
The students who are in Grade Three are going to climb the hill tomorrow.
3. 定語從句有時不直接緊靠先行詞，中間由一個定語、狀語或謂語隔開。
e.g. There is an expression in his eyes that I can’t understand.
4. 引導定語從句的關係副詞有時可以用“介詞 + which”來代替。
e.g. October 1, 1949 was the day on which ( = when ) the People’s Republic of China was founded.
5. 當定語從句中謂語動詞是帶介詞或副詞的固定短語動詞時，短語動詞的各個固定部分不要拆開。
e.g. The sick man whom she is looking after is her father.
6. 介詞在關係代詞前，只能用which和whom，且不能省略;介詞在句尾，關係代詞可有which, that, whom, 口語中也可用who，且可省略。
e.g. The man (whom/ who/ that) you were talking about has come to school.
(一)定語從句一般由關係代詞和關係副詞引導
1、關係代詞：who, whom, whose, which, that, as
2、關係副詞：when, where, why
關係代詞和關係副詞必須位於從句之首，主句先行詞之後，起著連線先行詞和從句的作用， 同時在從句中又充當句子成分。
e.g. She is the girl who sings best of all.(關係代詞who在從句中作主語)
The comrade with whom I came knows French.(whom在從句中作介詞with的賓語)
3、關係代詞和關係副詞的用法：1)當先行詞為人時用who 作主語，whom作賓語;2)當先行詞為物或整個句子時用which ，可作主語或賓語;3)先行詞為人、物時用that ，可作主語或賓語;4)whose用作定語，可指人或物;5)關係副詞when(指時間，在定語從句中作時間狀語，where(指地點，在定語從句中作地點狀語)，why(指原因，在定語從句中作原因狀語)。
(二)限制性定語從句與非限制性定語從句
1、限制性定語從句：從句與主句關係密切，去掉從句，主句意義不完整，甚至不合邏輯。
e.g. I was the only person in our office who was invited.(去掉定語從句，意思就不完整)
2、非限制性定語從句：從句對先行詞關係不密切，去掉定從句，意思仍然完整。形式上用逗號隔開，不能that用引導。
e.g. Tom’s father, who is over sixty, still works hard day and night.(who引導非限制性定語從句，整個句子可分成兩句來翻譯)
(三)使用定語從句時特別注意的幾個問題
1、that與which的區別。
e.g. There is nothing that can prevent him from doing it. 沒有什麼能阻止他不幹那件事。
The first place that they visited in Guilin was Elephant Trunk Hill. 在桂林他們所參觀的第一個地方是象鼻山。
This is the best film that I have ever seen. 這部電影是我看過的最好的一部。
Mr Smith is the only foreigner that he knows. 史密斯先生是他認識的唯一的外華人。
2)用which而不用 that的情況：
①引導非限制性定語從句;
②代表整個主句的意思;
e.g. He had failed in the maths exam, which made his father very angry. 他數學考試沒有及格，這使他的父親很生氣。
This is the room in which my father lived last year. 這是父親去年居住過的房子。
3)as引導定語從句時的用法
①as引導限制性定語從句通常用於the same … as, such … as結構中。
e.g. I want the same shirt as my friend’s. 我要一件跟我朋友一樣的襯衫。
Such machines as are used in our workshop are made in China. 我們車間使用的這種機器是中國製造的。
②as引導非限制性定語從句既可放在主句之前，也可放在主句之後，用來修飾整個句子。通常用下列句型：as is known to all, as is said, as is reported, as is announced, as we all know, as I expect 等。
e.g. As I expected, he got the first place again in this mid-term examination. 正如我所預料的那樣，他在這次期中考試中又獲得了第一名。
4)as 引導非限制性定語從句時與which的區別
①當主句和從句語義一致時，用as;反之，用which來引導非限制性定語從句。
e.g. He made a long speech, as we expected.
He made a long speech, which was unexpected.
②當非限制定語從句為否定時，常用which引導。
e.g. Tom drinks a lot every day, which his wife doesn’t like at all.
2. 關係代詞在從句中作主語時，從句的謂語動詞單數還是用複數應由先行詞決定。
e.g. The man who lives downstairs speaks English fluently. 住在樓下的那個人英語說得很流利。
The students who are in Grade Three are going to climb the hill tomorrow.
3. 定語從句有時不直接緊靠先行詞，中間由一個定語、狀語或謂語隔開。
e.g. There is an expression in his eyes that I can’t understand.
4. 引導定語從句的關係副詞有時可以用“介詞 + which”來代替。
e.g. October 1, 1949 was the day on which ( = when ) the People’s Republic of China was founded.
5. 當定語從句中謂語動詞是帶介詞或副詞的固定短語動詞時，短語動詞的各個固定部分不要拆開。
e.g. The sick man whom she is looking after is her father.
6. 介詞在關係代詞前，只能用which和whom，且不能省略;介詞在句尾，關係代詞可有which, that, whom, 口語中也可用who，且可省略。
e.g. The man (whom/ who/ that) you were talking about has come to school.