9.比较until和till

　此两个连词意义相同。肯定形式表示的意思是"做某事直至某时"，动词必须是延续性的。否定形式表达的意思是"直至某时才做某事"。动词为延续性或非延续性都可以。正确使用这两个连词的关键之一就在于判断句中的动词该用肯定式还是否定式。肯定句：I slept until midnight. 我一直睡到半夜时醒了。

　Wait till I call you. 等着我叫你。(在肯定句中可用before代替。例如 Let's get in the wheat before the sun sets.)

　 否定句：She didn't arrive until 6 o'clock. 她直到6点才到。

　　　　　 Don't get off the bus until it has stopped. 公共汽车停稳后再下车。

I didn't manage to do it until you had explained how. 直到你教我后，我才会做。

区别：1)until可用于句首，而till通常不用于句首。例如：

　　　　　　 Until you told me, I had heard nothing of what happened. 直到你告诉我以前，出了什么事我一点也不知道。

　　 2)until when 疑问句中，until要放在句首。例如：

　　　　　　　 ---Until when are you staying?　你呆到什么时候？

--- Until next Monday.　呆到下周一。　

注意：否定句可用另外两种句式表示。

1)Not until…在句首，主句用倒装。例如：

　Not until the early years of the 19th century did man know what heat is. 直到19 世纪初，人类才知道热为何物。

　Not until I began to work did I realize how much time I had wasted. 直到工作，才认识到我已蹉跎了几多岁月。

2)It is not until… that… 。例如：

　　 It was not until I began to work that I realized how much time I had wasted.

8. 比较while, when, as

1)as, when 引导短暂性动作的动词。例如：

　　 Just as / Just when / When I stopped my car, a man came up to me. 我一刹车，有一个人向我走来。

2)当从句的动作发生于主句动作之前，只能用when 引导这个从句，不可用as 或 while。例如：

　　 When you have finished your work, you may have a rest. 赶完活后，你可以休息一下。

3)从句表示"随时间推移"连词能用as，不用when 或while。例如：

　　 As the day went on, the weather got worse.　日子一天天过去，天气越变越坏。

7. 让步状语从句

1)though, although引导的让步状语从句，后面的从句不能有but，但是 though 和yet可连用。例如：

Although it's raining, they are still working in the field.　虽然在下雨，但他们仍在地里干活。

　　 He is very old, but he still works very hard. 虽然他很老了，但仍然努力地工作。

Though the sore be healed, yet a scar may remain. 伤口虽愈合，但伤疤留下了。(谚语)

2)　 as, though 引导的让步从句必须表语或状语提前(形容词、副词、分词、实义动词提前)。例如：

　　Child as /though he was, he knew what was the right thing to do. 虽然是个小孩，该做什么不做什么，他全知道。

3)　 ever if, even though　即使。例如：

　　 We'll make a trip even though the weather is bad. 即使天气不好，我们也要去远足。

4)　 whether…or…　不管……都。例如：

　　 Whether you believe it or not, it is true. 信不信由你，这确实是真的。

5)　"no matter +疑问词" 或"疑问词+后缀ever" 。例如：

　　 No matter what happened, he would not mind. =Whatever happened, he would not mind. 不管发生什么，他不在意。

　　替换：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 不能引导主语从句和宾语从句。

6. 条件状语从句

　 　连接词主要有 if, unless, as/so long as, on condition that 等。if 引导的条件句有真实条件句和非真实条件句两种。非真实条件句已在虚拟语气中阐述。

　 unless = if not.　 例如：

　 Let's go out for a walk unless you are too tired. 如果不太累，我们去散散步。

　 If you are not too tied, let's go out for a walk.

典型例题

You will be late ___ you leave immediately.　

A. unless　 B. until　 C. if　D. or

　 答案A。句意：除非你立即走，否则你就回迟到的。可转化为 If you dong leave immediately, you will be late。B、D句意不对，or表转折，句子如为 You leave immediately or you will be late.　

5.结果状语从句

　结果状语从句常由so…that 或 such…that引导。so…that与such…that之间可以转换。例如：

　　 The boy is so young that he can't go to school. 这男孩年龄太小，不能上学。

　　 He is such a young boy that he can't go to school

4.目的状语从句

　 表示目的状语的从句可以由that, so that, in order that, lest, for fear that, in case等词引导。例如：

　 You must speak louder so that /in order that you can be heard by all. 你必须大点声，别人就能听见了。

　 He wrote the name down for fear that(lest) he should forget it. 他写下了这个名字以免以后忘记。

　 Better take more clothes in case the weather is cold. 最好多穿点衣服，以防天发冷。

3.原因状语从句

比较because, since, as和for：

1)because语势最强，用来说明人所不知的原因，回答why提出的问题。当原因是显而易见的或已为人们所知，就用as或 since。例如：

　 I didn't go, because I was afraid. 我不去是因为我怕。

　 Since /As the weather is so bad, we have to delay our journey. 天气那么糟，旅行推迟了。

2)由because引导的从句如果放在句末，且前面有逗号，则可以用for来代替。但如果不是说明直接原因，而是多种情况加以推断，就只能用for。例如：

　 He is absent today, because / for he is ill. 他今天缺席，因为他病了。

　 He must be ill, for he is absent today. 他一定病了，所以今天缺席。

2.方式状语从句

　方式状语从句通常由as, (just) as…so…, as if, as though引导。

1)as, (just) as…so…引导的方式状语从句通常位于主句后，但在(just) as…so…结构中位于句首，这时as从句带有比喻的含义，意思是"正如…"，"就像"，多用于正式文体。例如：

　 Always do to the others as you would be done by. 你希望人家怎样待你，你就要怎样待人。

　As water is to fish, so air is to man. 我们离不开空气，犹如鱼儿离不开水。

　Just as we sweep our rooms, so we should sweep backward ideas from our minds.

　 正如打扫房屋一样，我们也要扫除我们头脑中落后的东西。

2)as if, as though

　 两者的意义和用法相同，引出的状语从句谓语多用虚拟语气，表示与事实相反，有时也用陈述语气，表示所说情况是事实或实现的可能性较大。汉译常作"仿佛……似的"，"好像……似的"。例如：

　 They completely ignore these facts as if (as though) they never existed. 他们完全忽略了这些事实，就仿佛它不存在似的。(与事实相反，谓语用虚拟语气。)

　He looks as if (as though) he had been hit by lighting. 他那样子就像被雷击了似的。(与事实相反，谓语用虚拟语气。)

　 It looks as if the weather may pick up very soon. 看来天气很快就会好起来。(实现的可能性较大，谓语用陈述语气。)

　 说明：as if / as though也可以引导一个分词短语、不定式短语或无动词短语。例如：

　 He stared at me as if seeing me for first time. 他目不转睛地看着我，就像第一次看见我似的。

　He cleared his throat as if to say something. 他清了清嗓子，像要说什么似的。

　The waves dashed on the rocks as if in anger. 波涛冲击着岩石，好像很愤怒　

1.地点状语从句

　地点状语从句通常由where, wherever 引导。例如：

　Where I live there are plenty of trees. 我住的地方树很多。

　Wherever I am I will be thinking of you. 不管我在哪里我都会想到你。

　 状语从句修饰主句中的动词,形容词,副词等,在复合句中作状语.引导状语从句的关联词是从属连词.状语从句用陈述句语序,一般位于复合句的句首或句末.当从句在句首时,从句后常用逗号和主句相隔.状语从句根据其在句中的不同作用分别表示时间,地点,原因,目的,结果,条件,比较,让步,行为方式等.