1. 限定性定语从句与非限定性定语从句的区别 a 非限定性定语从句和主句的关系不十分密切，朗读时先行词部分一般用降调并稍做停顿，书写的时候多半用逗号分开。 b 非限定性定语从句能够修饰整个句子，限定性定语从句则不能。 c 非限定性定语从句与限定性定语从句的含义不一样，限定性定语从句是确指，而非限定性定语从句是泛指。 d 先行词为专有名词或者具有特指对象的名词时，一般要用到非限制性定语从句。e 在非限定性定语从句中，现行词指人的时候，关系代词只能是who,whom，不能用that；先行词指物的时候，关系代词只能用which,不能用that。
2. 各种关系代词的使用方法a 关系代词who的用法 i. who 的前行词必须是人，在从句中可以担任主语，往往也可以代替在从句中担任宾语的whom,但是它前边不能有介词，如果带了介词就必须用宾格的whom: （介词+whom）
This is the teacher who teaches us mathematics. She is the girl who (whom I met at the party.（可以替代）She is the girl whom (who I went there with.（可以替代）She is the girl with whom I went there.（不可替代） ii. who，that在很多情况下可以通用，但是有些情况只能用who: 1. 先行词是one, ones, anyone的时候宜用who. One who has nothing to fear for oneself dares to tell the truth. The ones who flatter me don’t please me. Don’t tell anyone about the news who oughtn’t to know it.Anyone who fails to finish the task given should be criticized. 2. 先行词为those的时候，宜用who为关系代词 Those who were not fit for their work could not see the beautiful clothes made of the magic cloth. Those who want to go to the Great Wall sign up here. 3. 当先行词有比较长的后置定语的时候 I met a foreigner in the street yesterday who could asked me questions in Chinese. 4. 一个句子中带有两个定语从句，其中一个定语从句的关系代词为that,另一个则用 who. The boy that you met last night is the group leader who studies very hard. 5. 在there be 开头的句子中 There is an old man who wants to see you. There are many young men who are against him. b 关系代词whose的用法 whose是代词的所有格，它既可以代人也可以代物。当代物的时候，它相当于of which. I saw a woman whose bag was stolen. I’ll call a person whose father knows you. Which is the car whose owner you know? (Which is the car the owner of which you know Please show me the book whose cover is red. (Please show me the book the cover of which is red c 关系代词that的用法 首先特别注意，that只能用在限定性定语从句中，在非限定性定语从句中永远不能选用that, 另外介词后边也不可用that, 而是跟which. 在限定性定语从句中，which和that在代替物的时候，一般可以通用。The money that (which is in the wallet is mine. 有些情况下，只宜用that,而不宜用which i. 先行词是最高级形容词或者它前面有最高级形容词的时候 This is the best that has been used against pollution. English is the most difficult subject that you will learn during these years. ii. 先行词是序数词，或者它前面有一个序数词的时候 He is the last person (that I want to see. It is the first American movie of this kind that I’ve ever seen.iii. 主句已有疑问词who或者which的时候 Which is the bike that you lost? Who is the woman that was praixed at the meeting? iv. 先行词既有人又有物，宜用that Do you know the things and persons that they are talking about? The bike and its rider that had run over an old man were taken to the police station. v. 先行词是all, much, little, something, everything, anything, nothing, none, the one等不定代词时 You should hand in all that you have. We haven’t got much that we can offer you. I mean the one that you talked about just now. vi. 先行词前面Only, any, few, little, no, all, one of, the same, the very 等词修饰的时候 The only thing that we can do is to give you some money. Li Ming is the only one that wants to be a teacher. Li Ming is one of the students that want to be teachers in our class. vii. 有两个定语从句，其中一个关系代词已用which, 另外一个宜用that. Edison built up a factory which produced things that had never been seen before.
d 关系代词which的用法 在非限定性定语从句中，只宜用which, 不宜用that. Beijing, which is the capital of China, is a very beautiful city. 在限定性定语从句中which和that在指代物的时候常常可以通用，但是有时只宜用which 而不用that i. 关系代词前面有介词的时候 This is the hotel in which you will stay. ii. 如果有两个定语从句，其中的一句的关系词是that, 另一句宜用which. Let me show you the novel that I borrowed from the library which was newly open to us. 3. 关系代词与介词，关系代词的省略 a 关系代词和介词 介词放在关系代词的前面时，介词短语只能用which代物，和用whom代人 This is the hero of whom we are proud. I want to find the very pen with which I wrote that letter. 当介词放在句子的末尾时，可用that/which代物，that/whom/who来作为介词的宾语，且这个做介词宾语的关系代词往往忽略 This is the hero that (who/whom/忽略 we are proud of. b 关系代词的省略 首先注意只有限定性定语从句才能省略，非限定性定语从句绝对不能省略。在下列情况下，可以省略关系代词。 i. 当关系代词在从句中担任动词宾语的时候 The people (who we met at the party were very friendly to us. ii. 关系代词在从句中作介词，而介词在句尾时Here is the man (that you have been looking for. iii. 关系代词在从句中作表语时 Shang Hai is no longer the city (that it used to be. iv. 在there be句型中，和先行词为way时，关系代词总是省略 There is an old man (who wants to see you. I don’t like the way (that you talk to somebody else.
注意，有些动词+介词所组成的短语动词，关系非常紧密，介词不能前置
4. 定语从句注意事项 a one of + 复数名词+关系代词+复数型动词 the (only one of + 复数名词+关系代词+单数型动词 The Great Wall is one of the world-famous buildings that draw lots of visitors. Titanic is the (only one of the most wonderful movies that has been produced in Hollywood.
