1)修饰人的定语从句
who 主语/宾语(口语中，可省略)
that 主语/宾语(可省略，前面不能有介词)
whom 宾语(前面没有介词时可省略)
whose 定语
Do you know the person to whom he is talking?
Do you know the person(whom/that) he is talking to?
He is the man (who/whom/that) you can rely on.
He is the man on whom you can rely.
Do you know the woman who(that) is watching TV?
You're the only one whose advice he might listen to.
The girls whose names were called stood up.
Here is the man (whom/that) you've been looking for.
He is a man on whom you can safely depend.
2)修饰物的定语从句
如果修饰的词是物，而它在定语从句中做主语，则可以用that和which.
如果修饰的词是物，而它在定语从句中做宾语，则可以用that(可省略，前面不能有介词)和which(前面没有介词时可省略)。
whose后接名词做定语。
She wasn't on the train which /that arrived just now.
The dog which/that was lost has been found.
This is the question about which we've had so much discussion.
This is the question(that/which) we've had so much discussion about.
The novel (that/which) he recommended is worth reading.(be worth doing;值得做某事)
当定语从句修饰的词是不定代词，如anybody， nobody， nothing等，或是有only， very， 形容词最高级等修饰的名词时，从句的关联词往往用that ， that作从句的主语或宾语，作宾语时常被省略。
Is there anything (that ) I can do for you?
All(that) you have to do is to close the door and wait for him.
This is one of the easiest questions that do not need answering.
There is no one in the world who/that does not make a mistake.
定语从句修饰的词是不定代词、only、very、形容词最高级关联词用that，如果that在从句中做宾语，则可以省略。
3)修饰时间、地点、原因的定语从句
修饰时间的用when，相当于相当于“介词+ which”，在句中做状语。
修饰地点的用where，相当于相当于“介词+ which”，在句中做状语。
修饰原因的一般情况下跟的都是reason，用why关联词引导定语从句。
He came last night when I was going to bed.
I know of a place where we can have lunch.
She's going home where she can rest.
Do you know the reason why I left early?
There's no reason why he should do so.
4)非限定性定语从句 非限定性定语从句中不能用关联词that.修饰人时用who， whose， whom; 修饰物时用which， whose;修饰地点和时间的名词，且作状语时分别用where， when.如：
Water， which is a clear liquid， has many uses.
Our guide， who is a Chinese ， is an excellent cook.
They will fly to Boston， where they can plan to stay for four days， and then go to New York.
He picked up the book， the cover of which had been torn.(tear-tore-torn 撕裂、撕碎)
He is our English teacher， whose wife is a manager in a big firm.
非限定性定语从句还可以修饰整个句子，关联词只能用which.
The activity was postponed， which was exactly what we wanted.
They have invited me to attend the party， which is very kind of them.
限定型定语从句，如果修饰物并做宾语，前面又有介词，只能用which. 但是如果定语从句修饰的是不定代词，或是only，very以及形容词最高级，只能用that.在非限定性定语从句中修饰物只能用which，修饰人只能用who.如果非限定性定语从句修饰整个句子，关联词只能用which.
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