原因状语从句.doc

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二、原因状语从句：
1、定义：在句中用来说明主句原因的句子叫原因状语从句。
2、常用引导词: because (因为), as (由于), since (既然), now (that) (既然)
3、时态：原因状语从句一般都是根据实际情况选用适当的时态。通常是主过从过，主现从现。
4、because, since和as的区别：
1) because引导的原因状语从句一般放于主句的后面，because从句位于句首时要用逗号分开，放在句末时，可不用逗号分开。because表示直接原因， 语气最强， 最适合回答why引导的疑问句。because of 也表示原因，但它后面不接从句, 只能接名词, 代词或动名词。注意：because 和so 不可同时出现在一个句子里。
① I do it because I like it. = I like it so I do it.
② We went by bus because it was cheaper. = It was cheaper so we went by bus.
③ He can’t go to school because of his illness.
2) since引导的原因状语从句一般放于主句之前表示已知的、 显然的理由(通常被翻译成“既然”= now that )， 较为正式， 语气比because弱。
① Since you are free today, you had better help me with my mathematics.
② Since you don't trust him, you should not employ him.
③ Now (that) you are grown up, you should not rely on your parents.
3) as 引导原因状语从句时表示附带说明的“双方已知的原因”，含有对比说明的意味， 语气比since弱， 较为正式， 位置较为灵活(常放于主句之前)。
① As it is raining, you’d better take a taxi.
② As you are tired, you had better rest.
③ I went to bed early, as I was exhausted.
4) for引导的是并列句表示原因但并不说明主句行为发生的直接原因， 只提供一些辅助性的补充说明， for引导的并列句只能放于主句之后并且必须用逗号将其与主句隔开。
① He could not have seen me, for I was not there.
② He seldom goes out now, for he is very old.

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三、目的状语从句：
1、定义：在句中用来作目的状语的句子叫目的状语从句。
2、常用引导词: so that (以便), in order that (以便)
3、时态：目的状语从句一般都是根据实际情况选用适当的时态。也通常是主过从过，主现从现。
4、目的状语从句应注意以下：
1) 目的状语从句中常含有can, could, may, might, should, will, would等情态动词。
I got up early so that I could catch the first bus.
2) 在口语中so可以引导目的状语从句。
We'll sit nearer the front so we can hear better.
3) in order that与in order to的区别：
① in order that +从句 = so that +从句
② in order to+ 动词原形 = so as to + 动词原形(不放于句首) = to+ 动词原形
I get up early in order to catch the early bus.
= I get up early in order that I can catch the early bus.

四、结果状语从句：
1、定义：在句中用来作结果状语的句子叫结果状语从句。
2、常用引导词: so … that (如此…以致…), such … that (如此…以致…)
3、时态：结果状语从句一般都是根据实际情况选用适当的时态。也通常是主过从过，主现从现。
4、结果状语从句的句型：
结果状语从句的从句部分是补充说明主句中谓语动词发生的结果的，通常位于主句之后。结果从句中通常不用情态助动词，但must, can, could除外。结果状语从句其规律由so与such的不同词性决定。such 是形容词，修饰名词或名词词组，so 是副词，只能修饰形容词或副词。 so 还可与表示数量的形容词many, few, much, little连用，形成固定搭配。

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1) so + 形/ 副+ that从句
① The boy is so young that he can't go to school.
② He speaks so fast that no one can catch him.
2) so + many/few（+复名）+ that从句
There are so many picture-story books that the boy won't leave.
3) so + much/ little（+ 不可数名词）+that从句
He gave me so little time that it was impossible for me to finish the work on time.
4) so+ 形+ a/an+ 单名+ that从句
It was so hot a day that they wanted to go swimming.
5) such+ a/an+ 形+单名+ that从句= so+ 形+ a/an+单名+ that从句
He is such a young boy that he can't go to school.
= He is so young a boy that he can't go to school.
6) such+ 形+ 复名/不可数名词+ that从句
① They are such fine teachers that we all hold them in great respect.
② It is such nice weather that I would like to go to the beach.
5、结果状语从句与简单句的转换：
1) so… that (从句为肯定句) = … 形/副 + enough + (for sb.) to do sth.
He is so old that he can go to school alone.
= He is old enough to go to school alone.
2) so… that (从句为否定句) = … too + 形/副 + (for sb.) to do sth.
The problem is so hard that I can’t work it out.
= The problem is too hard for me to work out.
= The problem isn’t easy enough for me to work out.
五、让步状语从句
1、定义：在句中用来表示“退一步说……”的句子叫让步状语从句。
2、常用引导词: although (虽然) = though（尽管，即使），no matter+疑问词=疑问词-ever（无论…），even if = even though（即使），whether... or …(不管是…还是…)等。
3、时态：让步状语从句的时态一般采用主过从过，主将从现的原则。
4、让步状语从句的注意点：
1) although/ though 不可与but连用(二者只选其一)，但可与still / yet连用。
① Although / Though he is very old, still he is quite strong.
② Although he was ill , he went to school. = He was ill but he went to school.

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2) no matter + 疑问词 = 疑问词-ever “无论…”(引导让步状语从句可互换)
① Whatever (= No matter what) happened, he would not mind.
② Whoever (= No matter who) you are, you must keep the law.
③ However (=No matter how) expensive it may be, I’ll take it.
注意：“no matter+ 疑问词” 结构只能引导让步状语从句，而 “疑问词-ever” 还可以引导名词性从句（主语从句，宾语从句，表语从句和同位语从句）。
④ I'll eat whatever (≠no matter what) you give me. (whatever引导宾语从句)
⑤ Whoever (≠no matter who) comes will be welcome.  (whoever 引导主语从句)
六、条件状语从句
1、定义：由引导词if或unless引导的状语从句叫做条件状语从句。
2、常用引导词: if (如果) , unless = if…not (如果不/ 除非) , so/as long as(只要)
3、时态：条件状语从句的时态常采用主将从现原则。
① I will come to see you if I have time.
② Let's go out for a walk unless you are too tired.
= Let's go out for a walk if you are not too tired.
③ You can't learn English well unless you work hard.
= You can't learn English well if you don’t work hard.
④ You may borrow my book as long as you keep it clean.
注意: “祈使句，+ and / or + 简单句”是一个固定句型，这里祈使句相当于一个由if引导的条件状语从句：用and引导的简单句常表示一个较好的结果，用or引导的简单句常表示一个不愉快或不理想的结果；谓语动词常用一般将来时。即：
① 祈使句，and + 简单句(一般将来时) = If you do sth, you’ll do sth.
(这个句型表示“如果做到了祈使句表示的事情，就会有后面句子表示的结果”。)
Think hard , and you’ll find a way. = If you think hard, you’ll find a way.
② 祈使句，or +简单句(一般将来时)= If you don’t do sth, you’ll do sth.
(这个句型表示“如果做不到祈使句表示的事情，就会有后面句子表示的结果”。)
Hurry up, or you’ll be late. = If you don’t hurry (up), you’ll be late.

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