(1)关系代词 e.g.:that,which,who,whom,whose etc.
(2)关系副词 e.g.:when,where,why etc.
The woman who is standing by the classroom is our Chinese teacher.
This is the room where Bin Ladin once lived.
The girl who plays the piano very well is his girlfriend.
She is no longer the woman who she used to be.
I can't remember the man who I gave the key to.
Where is the student whom Professor Nirth praised at the meeting.
The girl with whom he was traveling is his girlfriend.
注：在“介词提前”即“介词+关系代词”结构出现时，关系代词只能用 whom 和 which 。
She is looking after the little child whose parents have gone to Singapore.
He lived in the room whose windows face south.
The man that is speaking at the meeting is a famous scientist.
Is this the teacher that you talked about yesterday.
She is no longer the girl that she was in her childhood.
The train that has just left is for Beijing.
Is this the photo that you took last summer?
I wish my home town was not a polluted place that you think it to be.
The building which stands near the train station is a company.
The computer which she wanted to buy was sold out.
She was fond of dancing,which her husband never was.
When(=at,on,in,during + which):代替时间名词.做时间状语:
I shall never forget the day when(on which) we moved into our new flat.
Where(=in,at + which):代替地点名词.做时间状语:
This is the place where(at which) John parks his car.
She didn't know the reason why(for which) she was dismissed.
as用作关系代词和关系副词引导限定性定语从句,并在从句中做主语,宾语,表语或状语,构成:the...same as, such...as, so...as 等结构.
Here are such questions as are often asked by the university students.
This is the same T-shirt as I have bought.
She has never seen such a handsome boy as I am.
She'll do the experiment the same way as I do.
I came the same day as he left.
She studies in the same college as he does.
She didn't believe such reason as he did so.
Here is so difficult a question as nobody can answer.
(2)引导非限定性定语从句. as引导非限定性定语从句时,代替整个主句,对其进行说明.一般用于as we all know,as is known to all,as it is,as is said above,as already mentioned above,as is usual,as is often the case,as is reported in the newspaper等句式中.as引导非限定性定语从句中做主语,表语或宾语,且引出的从句位置比较灵活,可位于句首或句尾,也可插如入主句中间.通常由逗号将其与主句隔开.as此时有"正如...","就像..."之意.
As is known to China,Qu Yuan is a great Chinese poet.
He forgot to bring his textbook with him,as was often the case.
She is absorbed in work,as she often was.
As we all know,the moon is round.