原因状语从句

1、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。通常是主过从也主现从现。4、because, since 和 as 的区另U: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： becaus

2、e和so不可同时出现在一个句子里。 I do it because I like it. = I like it so I do it. We went by bus because it was cheaper. = It was cheaper so we went by bus. He can ' t go to school because of his 川ness.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。 Since you are free

3、today, you had better help me with my mathematics. Since you don't trust him, you should not employ him. 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）。 As it is raining, you ' d better take a taxi. As

4、 you are tired, you had better rest. 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。 He could not have seen me, for I was not there. He seldom goes out now, for he is very old.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 tha

5、t （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

6、区另U: in order that + 从句 =so that + 从句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,一以致一）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

7、 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。6.1) so +形/副+ that 从句 The boy is so young that he can't go to school. He speaks so fast tha

8、t no one can catch him.2) so + many/few (+复名)+ that 从旬There are so manypicture-story books that the boy won't leave.3) so + much/ little (+ 不可数名词)+that 从句He gave meso little time that it was impossible for meto finish the work on time.4) so+ 形 + a/an+ 单名 + that 从句It was so hot a day that they wa

9、nted to go swimming.5) such+ a/an+形 + 单名 + that 从旬= so+ 形 + a/an+ 单名 + that 从旬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 They are such fine teachers that we all hold them in great respect. It is such nice wea

10、ther 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 01d 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

11、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 （无论一） , even if = even though（即使）,whether. or （不管是一还是-）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

12、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。 Although / Though he is very old, still he is quite strong. Although he was 川，he went to school. = He was ill but he went to school.7.2） no matter + 疑问词=疑问词-ever“无论”（引导让步状语从句可互换） Whatever （= No matter what） happened, he would not mind. Whoev

13、er （= No matter who） you are, you must keep the law. 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）。 I'll eat whatever （* no matter what） you give me. （whatever引导宾语从句） Whoever （* no matter wh o） comes w

14、ill 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/aslong as （只要）3、时态：条件状语从句的时态常采用主将从现原则。 I will come to see you if I have time. Let's go out f or a walk unless you are too tired.=Let's go out for a walk if you are not too t

15、ired. You can't learn English well unless you work hard.=You can't learn English well if youdon' t work hard. 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： 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