語法概念
關系詞通常是用來引導定語從句的,但as,than和but這三個詞卻與which,who,that,where,when和why等典型的關系詞不同｡三者本身具有常見的字面意義,前面有名詞作先行詞,但後面的定語從句卻不像典型的定語從句｡這些既像連接詞又像關系詞的詞,我們就姑且稱它們為準關系詞｡下面對其逐個作一分析:
一､as作為準關系代詞出現在the same ... as, such ... as,和as ... as等結構中｡這時,as前面通常要有名詞;as後面的從句意義上不像是通常的定語從句;as需要在從句中充當一定的句子成分｡
1. the same ... as
1) as在從句中作主語
She is the same person as came here last Sunday. 她就是上星期天來這兒的那個人｡
2) as在從句中作賓語
This is the same watch as I lost while I was doing the sightseeing in Shanghai three months ago. 這塊表跟我三個月前在上海觀光時丢失的那塊一樣｡
3) as在從句中作be動詞的表語
China is not the same country as it used to be. 中國已今非昔比｡
4) as在從句中作行為方式狀語
You should learn to do housework in the same way as your mother does it. 你應該學會像你母親那樣做家務活｡
2. such ... as
1) as在從句中作主語
Let children read such books as tend to make them better and brighter. 讓孩子看那些容易讓他們變得更好更聰明的書｡
2) as在從句中作賓語
This is not such an interesting book as you just talked about. 這不是你們剛才談到的那種有趣的書｡
3) as在從句中作be動詞的表語
Such a bad man as he is will be punished. 像他這樣的壞人一定會受到懲罰｡
3.as ... as
1) 第二個as在從句中作主語
He has as much money as is required. 他要多少錢就有多少錢｡
2) 第二個as在從句中作賓語
I have as many friends as you (do). 我的朋友和你的朋友一樣多｡
3) 第二個as在從句中作be動詞的表語
As is known to all, Taiwan is one of the Chinese provinces。衆所周知,台灣是中國的一個省｡
二､than作為準關系詞出現在more ...than, less ...than,fewer ... than等結構中｡這時,than前面要有名詞; than本身有比較意義,而且需要在從句中充當一定的句子成分｡
1.than在從句中作主語
Take it casy; I have more money than is needed. 放心,我的錢比所需要的還多
2.than在從句中作賓語
I have more/fewer books than you (do). 我的書比你的多/少｡
3.than在從句中作be動詞的表語
He is a better boy than you (are). 他是一個比你更好的男孩｡
三､but作為準關系詞 本身含有否定意義,它前面的主句還有另一個否定意義｡這時but在意義上相當于“who...not ...”或“which/that ... not ...”｡
1.定語從句中有be動詞,并将其改為含but的複合句時,be動詞後面不能再有not
There is no one who is not conccrned about his future. (= There is no one but is concerned about his future.) 沒有人不關心自己的未來｡
2.定語從句中有can,will,shall,must,may,should,ought to等助動詞或情态動詞,在将其改為含but的複合句時,這些助動詞或情态動詞後面不能再有not
There is nothing that she can’t do. (= There is nothing but she can do.) 沒有她做不到的事｡
3. 定語從句中有助動詞do, does, did, 在将其改為含but的複合句時,應去掉do, does, did, 還原其後動詞的時态及人稱變化
There is no one who doesn’t wish to make great achievements. (= There is no one but wishes to make great achievements.) 誰都希望自己将來能有所成就｡
用法
一、關系代詞的用法
當先行詞指人時，若它在從句中作主語，則用who；若它在從句作賓語，則用whom或who；若它在從句中作定語，則用whose。如：
The man who told me this refused to tell me his name. 告訴我這事的人不肯告訴我他的名字。
The woman whose umbrella you took is very angry about it. 你拿了那個女人的傘，她非常生氣。
當先行詞指物時，若在定語從句中作主語或賓語，則用which；若它在定語從句中作定語用，則用of which或whose。如：
I saw something in the paper which might interest you. 我在報上看到一樣可能使你感興趣的東西。
He’s written a book the name of which (whose name) I’ve forgotten. 他寫了一本書，書名我給忘了。
二、關系副詞的用法
關系副詞主要有when, where, why等，在定語從句中作狀語，分别表示時間、在點和原因。when主要放在time, day, years, season, age, occasion等時間的名詞後；where主要放在place, city, town, village, house等地點名詞後；why則通常隻放在reason後。
Wednesday is the day when the shops are not open in the afternoon.星期三下午商店不開門。
Give me one reason why we should help you. 給我舉出一個我們應當幫助你的理由。
要特别注意，activity, case, point, even, situation, job, organization, position等抽象名詞後接where引導定語從句的用法(這是近幾年高考的一個新熱點)。如：
I don’t want a job where I’m chained to a desk all day. 我不想找一份整天坐辦公桌前的工作。
Today, we’ll discuss a number of cases where beginners of English fail to use the language properly. 今天，我們将讨論一些英語初學者對英語使用不當的問題。
The treatment will continue until the patient reaches the point where he can walk correctly and safely. 治療将會持續到病人可以正常且安全地行走。
If you risk something important, you cause it to be in a dangerous situation where you might lose it. 你如果拿重要的東西去冒險，那你就是将它置于一種可能會失去它的危險境地。
關系代詞that的用法
1）不用that的情況
a) 在引導非限定性定語從句時 (錯) The tree, that is four hundred years old, is very famous here.
b) 介詞後不能用 We depend on the land from which we get our food.
2) 隻能用that作為定語從句的關系代詞的情況
a)在there be 句型中，隻用that，不用which。
b)在不定代詞，如：anything, nothing, the one, all, much, few, any, little等作先行詞時，隻用that，不用which。
c)先行詞有the only, the very修飾時，隻用that。
d)先行詞為序數詞、數詞、形容詞最高級時，隻用that。
e)先行詞既有人，又有物時。
Finally, the thief handed everything that he had stolen to the police.那賊最終把偷的全部東西交給了警察。
不能用關系代詞Which的幾種情況
1.當先行詞為all, little, much, few, everything, none 等不定代詞時關系代詞用that而不用which.
There are few books that you can read in this book store.
2.當先行詞既有人又有物時,關系代詞用that, 不用which.
He asked about the factories and workers that he had visited.
3.當先行詞有形容詞最高級修飾時,關系代詞用that, 而不用which.
Guilin is one of the most beautiful cities that I have ever visited.
4.當先行詞有序數詞修飾時,關系代詞用that,不用which.
The first sight that was caught at the Great Wall has made a lasting impression on him.
5.當先行詞被the only, the very, the same, the right等修飾時,關系代詞用that,不用which.
It is the only book that he bought himself.
6.當先行詞被all, every, any, much, little, few, no等修飾時,關系代詞用that,不用which.
There is no clothes that fit you here.
7.當主句是以which開頭的特殊問句時,定語從句關系代詞一般用that而不用which.
Which of the books that had pictures was worth reading?
8.在強調句型" It is ... that ..." 中,隻用that,不用which.
It is in this room that he was born twenty years ago.
9.在" such (the same) ... as ..." 句型中,關系代詞要用as,而不用which.
We need such materials as (not which) can bear high temperature.
10.表示"正如... 那樣","正象..."之意時,用as,不用which.
Mary was late again, as had been expected.
11.As引導的定語從句可以放在主句前面,也可以放在主句後面或主句中間,而由which引導的定語從句隻能放在主句後面。
As we all know, oceans cover more than 70% of the earth.
used to/be used to的分别
used to+do："過去常常"表示過去習慣性的動作或狀态，但如今已不存在。
Mother used not to be so forgetful.
be used to + doing： 對……已感到習慣，或"習慣于"，to是介詞，後需加名詞或動名詞。
Scarf is used to taking a walk.(現在習慣于散步)
used to的用法（否定式簡寫為usedn't）過去經常，以前常常
This used to be a shabby house. （此房年久失修）
used to,would這兩個詞語都可以表示過去常做某事，有時可以換用。used to do強調整過去習慣性的行為或狀态，但是現在沒有這種行為或狀态了。因此，這個短語的内涵是今昔對比。
關系代詞的不可省略和可以省略
1.關系代詞which,whom,who,that在定語從句中作賓語時可以省略。
Here is the man (who/that/whom)you're been looking for.
以下情況不能省略
（1）在介詞+whom與介詞+which中，whom,which不能省略。
That is the headmaster with whom my father was talking just now.
（2）在非限制性定語從句中，作賓語的關系代詞也不能省略。
The elephant is like a spear,as anybody can see.
（3）在the same ...as,such...as,as...as,the same...that中，as,that即使作賓語，也不能省略I have bought the same bicycle as you have (bought).(指同類用as)
This is the same book that I read the day before yesterday.(that指同一個)
（4）當由and,but,or等連詞連接兩個或兩個以上的定語從句修飾一個先行詞時，第一個關系代詞可省，但第二，第三個不可省略。
This is the book (which) I read yesterday and which I find very interesting.
2.當that在從句中作補語時可以省略。
She is all (that) a teacher should be.
3.在there be 結構中出現定語從句，或在定語從句中出現there be時，用作主語的關系代詞也可省略。
This is the best dictionary (that) there is in the library.
狀語的省略
（1）當先行詞是reason，而且定語從句中作原因狀語時，關系代詞可用why,that,也可以省略。
That is the reason (why) I did it.
（2）當先行詞是way,且在定語從句中作方式狀語時，關系代詞可用in which,that,也可以省略。
I don't know the way that/ which leads to the top of the mountains.
(3)當先行詞是time時，關系代詞可用when,that 或省略。
I don't know the exact time (when/that) the sports meet will take place.
注意：關系代詞作賓語有時也不能省略。
特殊代詞
but，as，than作關系代詞引導定語從句
but既可指人，也可指物，常在定語從句中充當主語。but本身含"否定"的意思，其作用相當于"that /which /who．．．not"。它前面的主句通常有"否定"的詞（如：no，not， little，few，hardly等）。but引導的肯定定語從句和否定的主句連用，達到強烈肯定的修飾效果。例如： There is no mother but loves her own children．（=There is no mother that/who does not love her own children．）沒有不愛自己孩子的母親。
as既可指人，也可指物，常在限制性定語從句中充當主、賓、表語。as引導的定語從句的先行詞前面常有as /such /the same等修飾詞。例如： ①He is as brave a man as ever lived．他是世界上最勇敢的人。 ②Don’tread such books as are not worth reading．不要讀那些不值得讀的書。 as作關系代詞，還可用來引導非限制性定語從句，as引導的定語從句可放在句首、句中或句末。例如： ① Taiwan，as we all know，is an inseparable part of China． ②As we all know，Taiwan is an inseparable part of China． ③Taiwan is an inseparable part of China， as we all know．
than既可指人，也可指物，可作關系代詞來引導定語從句。than前通常有表比較的詞。例如：Fewer friends than we had expected came to our evening party．來參加晚會的朋友比我們預料的還要少。
在使用上述三個特殊的關系代詞時，還要注意區分下列兩個詞組： 1．"such．．．that．．．"表"如此……以緻……"的意思，用來引導一個結果狀語從句；而"such．．．as．．．"表"像……這（那）樣"的意思，用來引導定語從句，as在定語從句中充當主、賓、表語等。試比較下列兩個句子： ① He is such an honest man that we respect him．他是一個如此誠實的人以緻我們都尊敬他。 ② He is such an honest man as we respect．他像我們所尊敬的那種誠實的人。 2．"the same．．．that．．．"表同一人或物，而"the same．．．as．．．"表同種類的東西。試比較下列兩個句子： ①This is the same book that I lost．這就是我丢失的那一本書。（指同一本書） ②This is the same book as I lost．我丢失的那一本書一模一樣。（并不是原來的那一本）
語法注意
1.常用that不用which的情況:
1）先行詞為all, anything, everything, nothing, something等時。
I will do all (that) I can to help you。
2）先行詞被序數詞、形容詞最高級或the only, the very等所修飾時。
He was the only person that joined the army in his village that year.
3）先行詞既有人,又有物時
They talked about the people and the things (that)they remembered in the school。
4）當主句是以who 或which開頭的疑問句時, 定語從句用that 引導, 以避免重複。
Who is the boy that was here just now?
2.若被修飾的名詞充當從句介詞賓語時
介詞可提前于引導詞之前,此時的引導詞隻能用whom 或which。
The pencil with which he was writing broke。
3.當先行詞為way時
其後的定語從句用in which或 that引導,也可不用引導詞。
I don’t like the way (in which/that) he talks to me。
