定語從句是英語中常見的句型，而關系詞：when,where,who,which，that等的用法又是定語從句中的高頻考點，為了方便考生們更好的掌握，庫課小編今天就來給大家分享定語從句中關系詞的用法，一起看看吧。
1.who
當先行詞是指人得名詞或代詞，而且關系詞在句中作主語時，選who。
The boy who is standing over there is Tom.
He who doesn’t reach the Great Wall is not a true man.
2.whom
當先行詞是指人得名詞，而且關系詞在句中作主語時，選whom。
This is our English teacher whom everybody likes.
3.whose
?、?當先行詞是指人的名詞，而且關系詞在句中作定語時，選whose。
This is my deskmate whose father works in a factory.
?、?當先行詞是指物的名詞，而且關系在句中作定語時，選whose。
We study in a classroom whose windows face to the south.
4.that
?、?當先行詞是指物的名詞，關系詞在句中作主語時，選that。
This is a machine that can walk.
② 當先行詞是指物的名詞，關系詞在句中作賓語時，選that。另外，that可以省略。
I like the present (that) my father sent me.
?、?當先行詞是指人的名詞，關系詞也可選用that=who。
The boy that/who is playing football on the play ground is my brother.
5.which
當先行詞是指物的名詞時，關系詞也可選用which，它在句中作主語或賓語，which=that。
6.下列情況下，關系詞只能選用that
?、?當先行詞為不定代詞 something, anything, nothing, everything時。
Is there anything that I can do for you?
?、?當先行詞為不定代詞all時。
Mr. Li does all that he can to do his work well.
?、?當先行詞被all, some, any修飾時。
These are all the things that I have done today.
④ 當先行詞被the only, the very 修飾時。
This is the only computer that he often turns to for help.
⑤ 當先行詞被序數詞，形容詞最高級修飾時。
This is the cleaning room that you can see here.
?、?time 作先行詞，前面有序數詞或last修飾時。
This is the last time that I’ll give you pocket money.
?、?盡管先行詞指人，但關系詞在句中作表語時。
He is no longer the child that he used to be 20 years ago
?、?以 who開頭的特殊疑問句，盡管先行詞指人。
Who is the person that is sitting on the ground ?
⑨ 當先行詞包括人和物時。
7. 下列情況下，關系詞只能選which
?、?在非限制性定語從句中。
This is my favorite pen, which I bought yesterday.
?、?先行詞不是一個詞，而是前面整個句子的概念時。
The boy is very polite, which makes his parents happy.
?、?當先行詞指物，用“介詞+which”。
This is the pen with which I often write.
8. as
As 引導定語從句時，有四種情況。As在句中作主語，賓語。
?、?as 單獨引導定語從句。
As we all know (=As is known to us all), Yao Ming is a famous basketball player.
?、?the same …as… 與…一樣。
I have the same idea as you.
?、?such… as… 和…一樣。
Don’t read such a book as you can’t understand.
?、?as…as… 和…一樣。
In this library, you can borrow as many books as you can.
9. where
① 當先行詞是指地點的名詞，而且關系副詞在句中作狀語時，選where，where=介詞+which。
This is the classroom where we study.
?、?盡管先行詞是指地點的名詞，但關系詞在句中作主語，賓語時，只能選that/which。
This is the factory that/which makes paper.
This is the factory(that/which) we visited yesterday.
?、?盡管先行詞是指地點的名詞，關系詞在句中作主語，賓語，但非限制性定語從句只能用which。
This is the school, which he visited.
?、?the one 是代詞，代替前面的名詞，其后的that/which 往往省略。
Is this factory the one you visited?
⑤ 當situation, job, mark, race, point 等模糊概念的名詞，關系詞在句中作狀語時，選where。
You’d better make a mark where you have any questions.
?、?盡管先行詞是指地點的名詞，關系詞在句中作狀語，但定語從句末有介詞時，選which。
This is the lab which we do experiments in.
10.when
① 當先行詞是指時間的名詞，而且關系副詞在句中作狀語時，選when，when=介詞+which。
We will never forget the days when we stayed with Mr. Smith.
② 盡管先行詞是指時間的名詞，但關系詞在句中作主語，賓語時，選that或which。
Monday is the day which/that comes before Tuesday.
We will never forget the days (that/which) we spent with him.
?、?盡管先行詞是指時間的名詞，關系詞在句中作主語，賓語，但非限制性定語從句只能選which。
Wednesday is the day, which comes before Thursday.
?、?one 作替代詞，代替前面表示時間的名詞，其后的that/which往往省略。
That was an exciting moment, one I will remember forever.
?、?time作先行詞，前面有序數詞或last時，只能選that。
Is this the third time that you have been late for school this week?
11.why
?、?當先行詞是指表示原因的名詞reason時，如果關系副詞作狀語，選why，why=for which。
This is the reason why I didn’t attend the meeting yesterday.
?、?當先行詞是表示原因的名詞reason時，如果關系副詞在句中作賓語，選that/which,也可省略。
My parents didn’t believe the reason (that/ which) I give him.