二、原因状语从句：、定义：1在句中用来说明主句原因的句子叫原因状语从句。
: 、常用引导词2now (that)becauseas since(既然(既然),) (因为), ), (由于、时态：3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。
①I do it because I like it. = I like it so I do it.②We went by bus because it was cheaper. = It was cheaper so we went by bus.③He 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”=弱。
语气比because 较为正式，now that )，①Since you are free today, you had better help me with my mathematics.②Since you don't trust him, you should not employ him.③Now (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)。
①As it is raining, you'd better take a taxi.②As you are tired, you had better rest.③I 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。
①He could not have seen me, for I was not there.②He seldom goes out now, for he is very old.5.三、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in order that so that )以便(以便),(、时态：3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。
、目的状语从句应注意以下：4等情态动词。
1) 目的状语从句中常含有can, could, may, might, should, will, wouldI got up early so that I could catch the first bus.可以引导目的状语从句。
2) 在口语中soWe'll sit nearer the front so we can hear better. 的区别：3) in order that与in order to= so that +in order that + ①从句从句= to+ = so as to +in order to+ ②) 动词原形动词原形( 动词原形不放于句首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 such …that ) 以致…),以致…(如此…(如此…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。
连用，形成固定搭配容词many, few, much, little6.1) so + 形/ 副+ that从句①The boy is so young that he can't go to school.②He 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.从句形+ a/an+单名+ that+5) such+ a/an+ 形单名+ that从句= so+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.不可数名词+ that从句6) such+ 形+ 复名/ They are such fine teachers that we all hold them in great respect. ①②It is such nice weather that I would like to go to the beach.、结果状语从句与简单句的转换：5+ enough + (for sb.) to do sth. 形/副1) so…that (从句为肯定句) = …He is so old that he can go to school alone.= He is old enough to go to school alone.+ (for sb.) to do sth. 形/副2) so…that (从句为否定句) = …too +t work it out. The problem is so hard that I can'= The problem is too hard for me to work out.t easy enough for me to work out.= The problem isn'五、让步状语从句、定义：1的句子叫让步状语从句。
退一步说……”在句中用来表示“: 、常用引导词2although (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。
①Although / Though he is very old, still he is quite strong.②Although he was ill , 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)①Whatever (= No matter what) happened, he would not mind.②Whoever (= No matter who) you are, you must keep the law.③However (=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）。
④I'll eat whatever (≠no matter what) you give me. (whatever引导宾语从句)⑤Whoever (≠no matter who) comes will be welcome.??(whoever 引导主语从句)六、条件状语从句1、定义：引导的状语从句叫做条件状语从句。
unless或if由引导词2、常用引导词:ifunless = if…notso/as long as(只要) , ) (如果不(如果) , / 除非3、时态：条件状语从句的时态常采用主将从现原则。
①I will come to see you if I have time.②Let's go out for a walk unless you are too tired.= Let's go out for a walk if you are not too tired.③You can't learn English well unless you work hard.= You can't learn English well if you don't work hard.④You 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。