職稱英語重點語法講解--狀語從句
導語：狀語從句指句子用作狀語時，起副詞作用的句子。它可以修飾謂語、非謂語動詞、定語、狀語或整個句子。以下是小編為大家精心整理的職稱英語重點語法講解--狀語從句，歡迎大家閱讀參考!
一、狀語從句的概念和類別
狀語從句指句子用作狀語時，起副詞作用的句子。它可以修飾謂語、非謂語動詞、定語、狀語或整個句子。根據其作用可分為時間、地點、原因、條件、目的、結果、讓步、方式和比較等從句。狀語從句一般由連詞(從屬連詞)引導，也可以由詞組引起。從句位于句首或句中時通常用逗號與主句隔開，位于句尾時可以不用逗號隔開。
二、考點聚焦
1、時間狀語從句
(1)as、when、while用法
as表示“當……的時候”，往往和when/ while通用，但它著重強調主句與從句的動作或事情同時或幾乎同時發生。
She came up as I was cooking.(同時)
The runners started as the gun went off.(幾乎同時)
when:(at or during the time that )既可以表示在某一點的時候，又可表示在某一段時間內，主句與從句的動作或事情可以同時發生也可以先后發生。
It was raining when we arrived.(指時間點)
When we were at school, we went to the lipary every day.(在一段時間內)
while意思是“當……的時候”或“在某一段時間里”。主句中的動作或事情在從句中的動作或事情的進展過程中發生，從句中的動詞一般要用延續性動詞。在when表示a period of time時，兩者可以互換。
Please don’t talk so loud while others are working.
He fell asleep while/when reading. Strike while the iron is hot.(用as或when不可，這里的while意思是“趁……”)
(2)引導時間狀語從句的連接詞除上述外還有：
①till, not … until …, until, before, since
Don’t get off the bus until it has stopped.
He waited for his father until(till)it was twelve o’clock.
It will be five years before he returns from England.
②hardly / scarcely … when, no sooner … than, as soon as once
表示“一……就”
As soon as I have finished it , I’ll give you a call.
Once you show any fear, he will attack you.
We had hardly got / Hardly had we got into the country when it began to rain.
No sooner had he arrived / He had no sooner arrived than she started complaining.
③directly, immediately, the moment, the minute that… 一……就
He made for the door directly he heard the knock.
�、躤ach time, every time, by the time
Each time he came to my city, he would call on me.
注意：表示未來情況，主句用將來時，從句用現在時。
2、讓步狀語從句
(1)although與though可以引導讓步狀語從句，不能與but連用，但可以與yet連用。
Although they are poor,(yet)they are warm-hearted.
(2)even if或even though引導讓步狀語從句，表示“即使”，“縱然”，用來使人注意下文所強調內容的性質。
I’ll get there even if(though)I have to sell my house to get enough money to go by air.
(3)no matter后接上who、what、where、how等疑問詞，也可以在這類疑問詞后面加上ever構成whoever、whatever、wherever、however等。
Don’t trust him, no matter what / whatever he says.
Whoever peaks the law will be published.
No matter how hard the work is, you’d better try to do it well.
(4)as也可以引導讓步狀語從句。要用倒裝。
Child as(though)he is, he knows a lot.
Much as I like it, I won’t buy.
Try as he would, he couldn’t lift the heavy box.
3、原因狀語從句：because, for, as, since, now that
(1)表示不知道的原因時用because,即說話人認為聽話人不知道，因此because從句是全句最重要的部分，通常它被置于主句之后。
You want to know why I’m leaving? I’m leaving because I’m full.
for雖然表示不知道的原因，但其語氣較because要弱得多，是可說可不說的話，它只能置于主句之后，這時，for是并列連詞。如果不是因果關系，而是對前面主句的內容加以解釋或推斷時，只能用for。如：It’s morning now, for the birds are singing.(很顯然，鳥叫不可能是“現在已是早上”的原因。)
(2)表示已經知道的原因時用as或since,即某種原因在說話人看來已經很明顯，或已為聽話人所熟悉，因此它是句中不很重要的部分。since要比as正式一些，它們通常被置于語句之前，但有時卻相反。
Seeing all of the children already seated, he said,“Since everyone is here, let’s start.”
(3)下列情況下只能使用because:
�、僭诨卮饂hy的問句時;②在用于強調句型時;③被not所否定時。
4、地點狀語從句：where, wherever
Make a mark wherever you have any questions.
We will go where the Party directs us.
5、目的狀語從句：that, so that, in order that
注意：目的狀語從句的謂語動詞常與情態動詞連用，否則可能是結果狀語從句。不可置于句首。
6、結果狀語從句：that, so that, so … that, such … that …
注意：so + 形容詞/副詞 + that從句;such + 名詞 + that從句。
7、方式狀語從句：as, as if(though)
I’ll do as I am told to.
It looks as if it is going to rain.
8、比較狀語從句：than, as
9、條件狀語從句：if, unless, so (as) long as, in case, once, a far as, on condition that.
注意if與unless的區別：不能用and連接兩個unless從句，即不能有… unless …,and unless … 。但if … not and if … not卻不受此限。
You won’t lose your weight unless you eat less and unless you exercise more.(×)
但可以說 … unless you eat less and exercise more.
10、注意狀語從句中從句的省略現象
(1)連接詞 + 過去分詞
Don’t speak until spoken to.
Pressure can be increased when needed.
Unless repaired, the washing machine is no use.
(2)連詞 + 現在分詞
Look out while crossing the street.
(3)連詞 + 形容詞/其他
常見的有 it necessary、 if possible、 when necessary、 if any等。
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