从 句
(一)定语从句
(1)as可引起定语从句，常和such, same连用，有时可代表主句所表达的内容，译作“这一点”、“这件事”。
A. My hometown is no longer the same as it was.
B. Such people as you describe are very common now.
C. This elephant is like a snake, as anybody can see.
D. As is announced in the papers, our country has launched another man-made earth satellite.
(2)表示地点的名词、表示时间的名词和表示原因的名词作先行词时，关系词不一定是where, when和why。如果它们在定语从句中充当主语或宾语时，则应用which。
I'll never forget the day when you said good-bye to me.
A.
October 1st, 1949 is a day which the Chinese people will never forget.
This is the room where he was born.
B.
This is the room which he bought four weeks ago.
This is the reason why she was absent yesterday.
C.
This is the reason which she gave for her absence yesterday.
(3)在定语从句中关系代词who, that, which等作主语时，谓语应与主句中先行词保持一致。
A. The man who is standing there looks worried.
B. Those who have seen the picture enjoy it very much.
He is one of those boys who are fond of music.
C.
He is the only one of those boys who is fond of music.
(4)定语从句通常和所修饰的先行词紧紧相连，但是如果主句的谓语部分很短，那么定语从句可放在谓语部分后面以保持句子的平衡。
A new master will come tomorrow who will teach you German.
但要注意“我把昨天买的书放在桌上”这个句子。
正：I put the books which I bought yesterday on the desk.
误：I put the books on the desk which I bought yesterday.
(5)当有二个或二个以上分别表示人和物的先行词时，用that而不用who, whom, which。
The letter and the little boy that we had discovered disappeared again.
(二)状语从句
(1)注意连词as的一词多义：
A. He had to make a living by selling newspapers as he was only a little boy. (“当……的时候”，引导时间状语从句)
B. As he was not well, I decided to go without him. (“由于、鉴于”，引导原因状语从句)
C. He is not the same man as he used to be. (“正如”，定语从句)
D. Things are not always as they seem. (表语从句)
E. Young as he is, he knows a lot. (“虽然，尽管”，让步状语从句)
F. Please state the facts as they are. (“按照，如同”，方式状语从句)
G. The work is not so easy as you imagine. (“像……一样”，比较状语从句)
(2)表示条件的状语从句除由if和whether引导外，还可由unless, suppose, in case, so(as)long as, on condition(that), provided(that)引导，并注意在条件状语从句中不能用将来式。
A. We shall go outing unless it snows.
B. You'll get there in time so long as the bus doesn't break down.
C. You can borrow the book on condition that you do not lend it to anyone else.
D. Please remind me of it again tomorrow in case I forget.
E. Suppose he is absent, what shall we do?
F. I will go provided that my expenses are paid.
(3)whatever相当于no matter what, whenever相当于no matter when，以此类推，可引导让步状语从句。
Whatever happens, we're determined to fulfill the task.
A.
No matter what happens, we're determined to fulfill the task.
Whatever dictionary you have, lend it to me.
B.
No matter what dictionary you have, lend it to me.
注意：当whatever作名词性从句的连词时，就不能和no matter交换使用了。
正：Whatever she did is perfect.
误：No matter what she did is perfect.
正：Take whatever you want.
误：Take no matter what you want.
(4)where, when引导的从句，无先行词是状语从句，有先行词则是定语从句。
A. We'll go where the Party needs us. (地点状语从句)
We'll go to the place where the Party needs us. (定语从句)
B. He came when we needed help. (时间状语从句)
He came at a time when we needed help. (定语从句)
(5)while和when的区别
while和when都可作“当……的时候”解，都可引导时间状语从句。while后的从句中谓语动词只能用延续性动词，而when则瞬间动词和延续性动词都可用。
A. My mother entered the room while I was doing some sewing.
B. 正：When I had finished the work, I took a rest.
误：While I had finished the work, I took a rest.
While还可作“而，然而”解，when则没有这个意思。
A. Motion is absolute while stagnation is relative.
B. I am a late riser while my sister is an early bird.
when有时可作and then解，而while却不能。
A. I was wandering through the streets when I caught sight of a tailor's shop.
B. I went out for a walk, when I met John.
(6)though, when, while, if, till, until等引导的状语从句中的省略
当某些表示让步、方式、时间、条件的状语从句中的主语与主句中的主语相同，且谓语动词又包含be动词，那么这种状语从句中的主谓都可省略。
A. The article is very important though(it is)short.
B. When still a boy of ten(When he was still a boy of ten), he started working to support himself.
C. Do not leave the machine till told to do so(till you are told to do so).
D. If (he is) too old to work much, the retired worker is very enthusiastic about neighborhood affairs.
E. While (he was) in school, Kim worked hard to study his chosen subject, computer science.
F. He acted as if (he was) certain of success.
固定词组if(when, where)necessary(possible)是if(when, where) it is necessary (possible)的省略形式。
A. Fill in the blanks with proper articles where(it is) necessary.
B. Whenever possible (Whenever it was possible), one of them would stop him, make him stand at attention and ask him the three questions.
(7)if作“如果”解，引导状语从句，此时应注意从句中谓语动词不能用将来式；if作“是否”解，引导宾语从句，从句中该用什么时态就用什么时态。
A. I don't know if he will come tomorrow. (“是否”，宾语从句)
B. If he comes tomorrow, I'll tell him about it. (“如果”，状语从句)
(三)主语从句
(1)当主语从句在意义上和语法上都完整的情况下，连词必不可少。
A. That she was chosen made us very happy.
B. That theory must go hand in hand with practice is a principle we should always keep in mind.
当主语从句放在句首使句子显得笨重时，一般把它移到句子后面，前面用引导词it作形式主语。
A. It is strange that he didn't come yesterday.
B. It's not your fault that this has happened.
(2)表示“是否”的主语从句用whether引导，一般不用if引导。
A. Whether or not she will go is up to her to decide.
B. It is not yet known whether they will send a delegation to the conference.
(3)由连接代词(what除外)或连接副词引起的主语从句，可以直接放在句首作主语，也可放到句子后面，前面用it作形式主语。
When we shall have our discussion is still a question.
It is still a question when we shall have our discussion.
但如果句子是疑问形式，就只能用带it的结构了：
Has it been announced who will take part in this important job?
(4)无论主语从句有多长，一般作单数处理。
A. Whether we do it this or that way doesn't matter too much.
B. That you have achieved so much in such a short time is really something unthinkable.
(四)表语从句
(1)系动词后面的从句是表语从句。除be动词以外，常用的系动词还有：
A. 单纯表示一个特征或状态：feel, look, sound, taste, smell, seem, appear;
B. 表示由一种状态变为另一种状态：become, turn, get, grow, fall, go, come, run;
C. 保持某种状态：remain, continue, stay, keep, prove
(2)引导表语从句的连词是that, whether和as if
A. The fact remains that we are still behind the other classes.
B. The question is whether it is worth doing.
C. It looked as if it was going to snow.
(3)请注意“他没来学校的原因是因为他病了”这个句子。
误：The reason why he doesn't come to school is because he is ill.
正：The reason why he doesn't come to school is that he is ill.
(五)宾语从句
(1)宾语从句在双宾语中充当直接宾语。
A. Please advise me which book I should read first.
B. Mr. Smith explained to them that John had told him all about his past when he asked for a job in his factory.
C. You may ask the policeman how you can get to the Shanghai Indoor Stadium.
(2)在介词后面的宾语从句。
A. The Emperor was pleased by what the Prime Minister told him about the cloth.
B. The Swede stood quite still, except that his lips moved slightly.
C. The study also showed that, contrary to what many people believe, if you skip breakfast, you will not lose weight.
(3)带复合宾语的从句中，that引导的从句常常移到后部去，前面用it作形式宾语。
A. I took it for granted that they were not coming.
B. We all thought it a pity that our team should have lost the game.
C. They want to make it clear to the public that they do an important and necessary job.
(4)陈述部分带that从句作宾语时，作反意问句的疑问尾句应与主句的主谓保持一致。
A. I have told him many times that he should observe traffic regulations, haven't I?
B. You never told us why you were late for the last meeting, did you?
当陈述部分的主句是I think(suppose, believe, expect, imagine)时，反意问句的疑问尾句往往与that从句中的主谓保持一致。
A. I don't suppose he cares, does he?
B. I think you two have met before, haven't you?
(六)同位语从句
(1)同位语从句一般跟在某些名词(如idea, news, fact, promise, rumour, hope, belief,
thought, doubt, answer, message)后面，用以说明名词所表示的具体内容，用连词that或连接副词how, when, where等引导。
A. During the first hundred years of my stay in the sea, I made a promise that if anyone set me free I would make him very rich.
B. You have no idea how worried I was!
C. One of the men held the view that what the book said was right.
D. Braille had to face the fact that he would go to a special school for the blind in Paris.
(2)如果主句的谓语很短，为了保持句子平衡，可将谓语放在前面，而将同位语从句放在后面。
A. Several years later, word came that Napoleon himself was coming to inspect them.
B. News reached England that they were receiving little care.
(3)在on condition that, in spite of the fact that后的从句也是同位语从句。
A. I'll lend you this money on condition that you give it back in two months. B. He came to the meeting, in spite of the fact that he was very ill.
(4)定语从句和同位语从句的先行词都是名词，如果该引导词既在从句中充当成分，又能代替所修饰的先行词，则是定语从句；
如果该引导词在从句中不充当成分，或虽充当成分却不能代替所修饰的先行词，那么这个句子就是同位语从句。
He didn't tell us the date when he would start. (定语从句)
A.
I have no idea when he will start. (同位语从句)
Often, we read to discover facts that we didn't find in our first reading. (定语从句)
B.
The fact that he had not said anything surprised everybody. (同位语从句)
责任编辑：李芳芳