19.1 地点状语从句地点状语从句通常由where, wherever 引导。
Where I live there are plenty of trees.
Wherever I am I will be thinking of you.
19.2 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.
As water is to fish, so air is to man.
Just as we sweep our rooms, so we should sweep backward ideas from our minds.
2） as if, as though
They completely ignore these facts as if (as though) they never existed.
He looks as if (as though) he had been hit by lighting.
It looks as if the weather may pick up very soon.
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.
He cleared his throat as if to say something.
The waves dashed on the rocks as if in anger.
19.3 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。
I didn't go, because I was afraid.
Since /As the weather is so bad, we have to delay our journey.
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。
He is absent today, because / for he is ill.
He must be ill, for he is absent today.
19.4 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.
He wrote the name down for fear that(lest) he should forget it.
Better take more clothes in case the weather is cold.
19.5 结果状语从句结果状语从句常由so… that 或 such…that引导，掌握这两个句型，首先要了解so 和 such与其后的词的搭配规律。
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。
so foolish such a fool
so nice a flower such a nice flower
so many / few flowers such nice flowers
so much / little money. such rapid progress
so many people such a lot of people
（ so many 已成固定搭配，a lot of 虽相当于 many，但 a lot of 为名词性的，只能用such搭配。）
The boy is so young that he can't go to school.
He is such a young boy that he can't go to school
19.6 条件状语从句连接词主要有 if, unless, as/so long as, on condition that 等。.
unless = if not.
Let's go out for a walk unless you are too tired.
If you are not too tied, let's go out for a walk.
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.
19.7 让步状语从句though, although
注意： 当有though, although时，后面的从句不能有but，但是 though 和yet可连用
Although it's raining, they are still working in the field.
He is very old, but he still works very hard.
Though the sore be healed, yet a scar may remain.
1） ___she is young, she knows quite a lot.
A. When B. However C. Although D. Unless
2) as, though 引导的倒装句
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）。
Child as /though he was, he knew what was the right thing to do.
= Though he was a small child, he knew what was the right thing to do.
注意： a. 句首名词不能带任何冠词。
Try hard as he will, he never seems able to do the work satisfactorily.
= Though he tries hard, he never seems…
3) ever if, even though. 即使
We'll make a trip even though the weather is bad.
4) whether…or- 不管……都
Whether you believe it or not, it is true.
5) "no matter +疑问词" 或"疑问词+后缀ever"
No matter what happened, he would not mind.
Whatever happened, he would not mind.
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。
（错）No matter what you say is of no use now.
（对）Whatever you say is of no use now.
你现在说什么也没用了。(Whatever you say是主语从句)
（错）Prisoners have to eat no matter what they're given,
（对）Prisoners have to eat whatever they're given. 囚犯们只能给什么吃什么。
19.8 比较while, when, as1）as, when 引导短暂性动作的动词。
Just as / Just when / When I stopped my car, a man came up to me.
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。
When you have finished your work, you may have a rest.
As the day went on, the weather got worse.
19.9 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。
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 Let's get in the wheat before the sun sets.）
She didn't arrive until 6 o'clock.
Don't get off the bus until it has stopped.
I didn't manage to do it until you had explained how. 直到你教我后，我才会做。
Until you told me, I had heard nothing of what happened.
2)Until when 疑问句中，until要放在句首。
---Until when are you staying? 你呆到什么时候？
--- Until next Monday. 呆到下周一。
(1）Not until …在句首，主句用倒装。
Not until the early years of the 19th century did man know what heat is.
Not until I began to work did I realize how much time I had wasted.
(2) It is not until… that…
19.10 表示"一…就…"的结构hardly/scarcely…when/before, no sooner…than 和as soon as都可以表示"一…就…"的意思，例：
I had hardly / scarcely got home when it began to rain.
I had no sooner got home than it began to rain.
As soon as I got home, it began to rain.
注意：如果hardly, scarcely 或no sooner置于句首，句子必须用倒装结构：
Hardly / Scarcely had I got home when it began to rain.
No sooner had I got home than it began to rain.