復(fù)合句（Complex Sentence）由一個(gè)主句（Principal Clause)和一個(gè)或一個(gè)以上的從句(Subordinate Clause)構(gòu)成.
主句是全句的主體,通?？梢元?dú)立存在；從句則是一個(gè)句子成分,不能獨(dú)立存在.
從句不能單獨(dú)成句,但它也有主語(yǔ)部分和謂語(yǔ)部分,就像一個(gè)句子一樣.所不同在于,從句須由一個(gè)關(guān)聯(lián)詞（connective）引導(dǎo).
復(fù)合句（The Complex Sentence）：句子中有一個(gè)或一個(gè)以上的從句,叫做復(fù)合句.復(fù)合句可分為：
1).定語(yǔ)從句（The Attributive Clause）；
2).狀語(yǔ)從句（The Adverbial Clause）；
3).名詞性從句（The Noun Clause）
一、 定語(yǔ)從句
· 定語(yǔ)從句的定義
定語(yǔ)從句在句子中作定語(yǔ),用來(lái)修飾一個(gè)名詞、名詞詞組或者代詞.
· 先行詞和引導(dǎo)詞
被修飾的名詞、名詞詞組或代詞叫做先行詞；
在先行詞和定語(yǔ)從句之間起連接作用的詞叫做引導(dǎo)詞.
引導(dǎo)詞分為“關(guān)系代詞”和“關(guān)系副詞”.
· 關(guān)系代詞和關(guān)系副詞
關(guān)系代詞有：who, whom, whose, that, which, as.
關(guān)系副詞有：when, where, why. 注意：關(guān)系副詞里面沒(méi)有how.
如果要修飾方式,用that或in which引導(dǎo),或者不用引導(dǎo)詞.
I don’t like the way (that, in which) he eyed me.
我不喜歡他看我的那個(gè)樣子.
· 關(guān)系代詞：who
關(guān)系動(dòng)詞who在從句中主要作主語(yǔ),在非正式語(yǔ)體里who還可以作從句中的賓語(yǔ).
He is the man who wants to see you.
He is the man who I saw in the park yesterday.
· 關(guān)系代詞：whom
He is the man （whom） I saw in the park yesterday.
（whom在從句中作賓語(yǔ)）
· 關(guān)系代詞：whose
whose 用來(lái)指人或物,（只能用作定語(yǔ), 若指物,它還可以同of which互換）.
They rushed over to help the man whose car had broken down.
Please pass me the book whose cover is green. （of which the cover/the cover of which）
· 關(guān)系代詞：which（1）
which指物,在從句中作主語(yǔ)或賓語(yǔ),作賓語(yǔ)時(shí)在非正式語(yǔ)體中可以省略.
They needed a plant which didn't need as much water as rice.
The farm (which) we visited yesterday is located in the suburb of Beijing.
· 關(guān)系代詞：which（2）
當(dāng)在which和that面前進(jìn)行選擇的情況下,一般情況下要選which：
1.在非限制性定語(yǔ)從句中通常用which作引導(dǎo)詞,而不能用that做非限制性定語(yǔ)從句的引導(dǎo)詞.
2. 修飾整個(gè)主句.
I never met Julia again after that, which was a pity.
3. 修飾謂語(yǔ)部分.
He can swim in the river, which I cannot.
4. 介詞 + which
They are all questions to which there are no answers.
· 關(guān)系代詞：that（1）
that多用來(lái)指物,有時(shí)也可以用來(lái)指人；在從句中作主語(yǔ)或賓語(yǔ).指物的時(shí)候多用that,也可用which.
It’s a question that (which) needs careful consideration.
（指物,作主語(yǔ).）
Who is the man that is reading a magazine under the tree?
（指人,作主語(yǔ).）
The girl (that) we saw yesterday is Tom’s sister.
（指人,作賓語(yǔ),可省略.）
· 關(guān)系代詞：that（2）
在以下的情況中,只能用that作引導(dǎo)詞,而不能用which作引導(dǎo)詞.
1. 先行詞為all , everything, anything, nothing, little等不定代詞時(shí).
All (that) she lacked was training.
2. 先行詞被形容詞最高級(jí)修飾時(shí)
This is the best film that I have ever seen.
3. 先行詞被序數(shù)詞和the last修飾時(shí)
4. 先行詞中既有人又有物時(shí)
They talked about the teachers and the schools that they had visited.
5. 主句是含有who或which的特殊疑問(wèn)句,為了避免重復(fù)時(shí)
二、 狀語(yǔ)從句
1 地點(diǎn)狀語(yǔ)從句
地點(diǎn)狀語(yǔ)從句通常由where, wherever 引導(dǎo).
Where I live there are plenty of trees.
Wherever I am I will be thinking of you.
2 方式狀語(yǔ)從句
方式狀語(yǔ)從句通常由as, (just) as…so…, as if, as though引導(dǎo).
1） as, (just) as…so…引導(dǎo)的方式狀語(yǔ)從句通常位于主句后,但在(just) as…so…結(jié)構(gòu)中位于句首,這時(shí)as從句帶有比喻的含義,意思是"正如…","就像",多用于正式文體,例如：
Always do to the others as you would be done by.
你希望人家怎樣待你,你就要怎樣待人.
As water is to fish, so air is to man.
我們離不開(kāi)空氣,猶如魚(yú)兒離不開(kāi)水.
Just as we sweep our rooms, so we should sweep backward ideas from our minds.
正如打掃房屋一樣,我們也要掃除我們頭腦中落后的東西.
2） as if, as though
兩者的意義和用法相同,引出的狀語(yǔ)從句謂語(yǔ)多用虛擬語(yǔ)氣,表示與事實(shí)相反,有時(shí)也用陳述語(yǔ)氣,表示所說(shuō)情況是事實(shí)或?qū)崿F(xiàn)的可能性較大.漢譯常作"仿佛……似的","好像……似的",例如：
They completely ignore these facts as if (as though) they never existed.
他們完全忽略了這些事實(shí),就仿佛它不存在似的.（與事實(shí)相反,謂語(yǔ)用虛擬語(yǔ)氣.）
He looks as if (as though) he had been hit by lighting.
他那樣子就像被雷擊了似的.（與事實(shí)相反,謂語(yǔ)用虛擬語(yǔ)氣.）
It looks as if the weather may pick up very soon.
看來(lái)天氣很快就會(huì)好起來(lái).（實(shí)現(xiàn)的可能性較大,謂語(yǔ)用陳述語(yǔ)氣.）
說(shuō)明：as if / as though也可以引導(dǎo)一個(gè)分詞短語(yǔ)、不定式短語(yǔ)或無(wú)動(dòng)詞短語(yǔ),例如：
He stared at me as if seeing me for first time.
他目不轉(zhuǎn)睛地看著我,就像第一次看見(jiàn)我似的.
He cleared his throat as if to say something.
他清了清嗓子,像要說(shuō)什么似的.
3 原因狀語(yǔ)從句
比較：because, since, as和for
1） because語(yǔ)勢(shì)最強(qiáng),用來(lái)說(shuō)明人所不知的原因,回答why提出的問(wèn)題.當(dāng)原因是顯而易見(jiàn)的或已為人們所知,就用as或 since.
I didn't go, because I was afraid.
Since /As the weather is so bad, we have to delay our journey.
2） 由because引導(dǎo)的從句如果放在句末,且前面有逗 號(hào),則可以用for來(lái)代替.但如果不是說(shuō)明直接原因,而是多種情況加以推斷,就只能用for.
He is absent today, because / for he is ill.
He must be ill, for he is absent today.
4 目的狀語(yǔ)從句
表示目的狀語(yǔ)的從句可以由that, so that, in order that, in case等詞引導(dǎo),例如：
You must speak louder so that /in order that you can be heard by all.
Better take more clothes in case the weather is cold.
5 結(jié)果狀語(yǔ)從句
結(jié)果狀語(yǔ)從句常由so… that 或 such…that引導(dǎo),掌握這兩個(gè)句型,首先要了解so 和 such與其后的詞的搭配規(guī)律.
比較：so和 such
其規(guī)律由so與such的不同詞性決定.such 是形容詞,修飾名詞或名詞詞組,so 是副詞,只能修飾形容詞或副詞. so 還可與表示數(shù)量的形容詞many, few, much, little連用,形成固定搭配.
so foolish such a fool
so nice a flower such a nice flower
so many / few flowers such nice flowers
so much / little money. such rapid progress
so many people such a lot of people
（ so many 已成固定搭配,a lot of 雖相當(dāng)于 many,但 a lot of 為名詞性的,只能用such搭配.）
so…that與such…that之間的轉(zhuǎn)換既為 so與such之間的轉(zhuǎn)換.
The boy is so young that he can't go to school.
He is such a young boy that he can't go to school
6 條件狀語(yǔ)從句
連接詞主要有 if, unless, as/so long as, on condition that 等..
if 引導(dǎo)的條件句有真實(shí)條件句和非真實(shí)條件句兩種.非真實(shí)條件句已在虛擬語(yǔ)氣中闡述.
unless = if not.
Let's go out for a walk unless you are too tired.
If you are not too tied, let's go out for a walk.
7 讓步狀語(yǔ)從句
though, although
注意： 當(dāng)有though, although時(shí),后面的從句不能有but,但是 though 和yet可連用
Although it's raining, they are still working in the field.
3) ever if, even though. 即使
We'll make a trip even though the weather is bad.
4) whether…or- 不管……都
Whether you believe it or not, it is true.
5) "no matter +疑問(wèn)詞" 或"疑問(wèn)詞+后綴ever"
No matter what happened, he would not mind.
Whatever happened, he would not mind.
替換：no matter what = whatever
no matter who = whoever
no matter when = whenever
no matter where = wherever
no matter which = whichever
no matter how = however
注意：no matter 不能引導(dǎo)主語(yǔ)從句和賓語(yǔ)從句.
（錯(cuò)）No matter what you say is of no use now.
（對(duì)）Whatever you say is of no use now.
你現(xiàn)在說(shuō)什么也沒(méi)用了.(Whatever you say是主語(yǔ)從句)
（錯(cuò)）Prisoners have to eat no matter what they're given,
（對(duì)）Prisoners have to eat whatever they're given. 囚犯?jìng)冎荒芙o什么吃什么.
8 比較while, when, as
1）as, when 引導(dǎo)短暫性動(dòng)作的動(dòng)詞.
Just as / Just when / When I stopped my car, a man came up to me.
2）當(dāng)從句的動(dòng)作發(fā)生于主句動(dòng)作之前,只能用when 引導(dǎo)這個(gè)從句,不可用as 或 while.
When you have finished your work, you may have a rest.
3）從句表示"隨時(shí)間推移"連詞能用as,不用when 或while.
As the day went on, the weather got worse.
日子一天天過(guò)去,天氣越變?cè)綁?
9 比較until和till
此兩個(gè)連詞意義相同.肯定形式表示的意思是"做某事直至某時(shí)",動(dòng)詞必須是延續(xù)性的.否定形式表達(dá)的意思是"直至某時(shí)才做某事".動(dòng)詞為延續(xù)性或非延續(xù)性都可 以. 正確使用這兩個(gè)連詞的關(guān)鍵之一就在于判斷句中的動(dòng)詞該用肯定式還是否定式.
肯定句：
I slept until midnight. 我一直睡到半夜時(shí)醒了.
Wait till I call you. 等著我叫你.
（在肯定句中可用before代替 Let's get in the wheat before the sun sets.）
否定句：
She didn't arrive until 6 o'clock.
Don't get off the bus until it has stopped.
1)Until可用于句首,而till通常不用于句首.
Until you told me, I had heard nothing of what happened.
直到你告訴我以前,出了什么事我一點(diǎn)也不知道.
2)Until when 疑問(wèn)句中,until要放在句首.
---Until when are you staying? 你呆到什么時(shí)候?
--- Until next Monday. 呆到下周一.
注意：否定句可用另外兩種句式表示.
(1)Not until …在句首,主句用倒裝.
Not until the early years of the 19th century did man know what heat is.
直到19 世紀(jì)初,人類才知道熱能是什么.
Not until I began to work did I realize how much time I had wasted.
直到我開(kāi)始工作,我才認(rèn)識(shí)到了我已蹉跎了幾多歲月.
(2) It is not until… that…
10 表示"一…就…"的結(jié)構(gòu)
hardly/scarcely…when/before, no sooner…than 和as soon as都可以表示"一…就…"的意思,例：
I had hardly / scarcely got home when it began to rain.
I had no sooner got home than it began to rain.
As soon as I got home, it began to rain.
注意：如果hardly, scarcely 或no sooner置于句首,句子必須用倒裝結(jié)構(gòu)：
Hardly / Scarcely had I got home when it began to rain.
No sooner had I got home than it began to rain.
三、 名詞性從句
1）.賓語(yǔ)從句（The Object Clause）；
· 賓語(yǔ)從句
在句子中起賓語(yǔ)作用的從句叫做賓語(yǔ)從句.賓語(yǔ)從句的引導(dǎo)詞和主語(yǔ)從句的引導(dǎo)詞相同.賓語(yǔ)從句可以作及物動(dòng)詞的賓語(yǔ),作短語(yǔ)動(dòng)詞的賓語(yǔ),介詞的賓語(yǔ).
· 賓語(yǔ)從句：及物動(dòng)詞
Everybody knows that money doesn't grow on trees.
· 賓語(yǔ)從句：短語(yǔ)動(dòng)詞
Please go and find out when the train will arrive.
· 賓語(yǔ)從句：介詞的賓語(yǔ)
I am interested in what she is doing.
· 賓語(yǔ)從句：否定的轉(zhuǎn)移
I don't suppose you're used to this diet.
我想你不習(xí)慣這種飲食.
I don't believe she'll arrive before 8.
我相信她8點(diǎn)之前不會(huì)到.
2）.表語(yǔ)從句（The Predicative Clause）；
· 表語(yǔ)從句
在句子中起表語(yǔ)作用的從句叫做表語(yǔ)從句.表語(yǔ)從句的引導(dǎo)詞和主語(yǔ)從句的引導(dǎo)詞相同.
What the police want to know is when you entered the room.
This is what we should do.
That's why I want you to work there.
as if, as though, because也可用來(lái)引導(dǎo)表語(yǔ)從句.
She seems as if she had done a great thing.
It is because you eat too much.
· 虛擬語(yǔ)氣：表語(yǔ)從句
主語(yǔ)是idea, notion, proposal, suggestion, request等名詞時(shí),作表語(yǔ)從句的動(dòng)詞為原形動(dòng)詞或should+原形動(dòng)詞.
My suggestion is that we (should) go and help him.
Our only request is that this should be settled as soon as possible.
3）.同位語(yǔ)從句（The Appositive Clause）.
· 同位從句一般跟在某些名詞如answer(答案),hope(希望),fact(事實(shí)),belief (信仰),news(消息),idea(主意；觀念),promise(承諾),information(信息),conclusion(結(jié)論),order(命令), suggestion(建議),problem(問(wèn)題),thought (想法)等后面.例如：
I had no idea that you were here.
She told us her hope that she would become a pianist.
He made a promise that he would never come late.
· 同位語(yǔ)從句：whether
whether可以引導(dǎo)同位語(yǔ)從句,而定語(yǔ)從句不能用whether作為引導(dǎo)詞.
He hasn’t made the decision whether he will go there.
I have small doubt whether he is suitable for the job.
· 同位語(yǔ)從句：what
what可以引導(dǎo)同位語(yǔ)從句,而定語(yǔ)從句不能用what作為引導(dǎo)詞
I have no idea what he is doing now.
· 同位語(yǔ)從句：how
how可以引導(dǎo)同位語(yǔ)從句,而定語(yǔ)從句不能用how作為引導(dǎo)詞
It’s a question how he did it.
· 同位語(yǔ)從句和定語(yǔ)從句的區(qū)別（1）
同位語(yǔ)從句和先行詞是同等的關(guān)系；而定語(yǔ)從句是用來(lái)修飾先行詞,是從屬的關(guān)系.
· 同位語(yǔ)從句和定語(yǔ)從句的區(qū)別（2）
that在同位語(yǔ)從句中沒(méi)有詞義,不充當(dāng)句子成分；而在定語(yǔ)從句中充當(dāng)主語(yǔ)、賓語(yǔ)等句子成分.
· 同位語(yǔ)從句和定語(yǔ)從句的區(qū)別（3）
whether, what, how可以用來(lái)引導(dǎo)同位語(yǔ)從句；而它們不能用來(lái)引導(dǎo)定語(yǔ)從句.