2020年军队职称英语理工类语法备考：状语从句

一、状语从句的概念和类别

　　状语从句指句子用作状语时，起副词作用的句子。它可以修饰谓语、非谓语动词、定语、状语或整个句子。根据其作用可分为时间、地点、原因、条件、目的、结果、让步、方式和比较等从句。状语从句一般由连词(从属连词)引导，也可以由词组引起。从句位于句首或句中时通常用逗号与主句隔开，位于句尾时可以不用逗号隔开。

　　二、考点聚焦

　　1、时间状语从句

　　(1)as、when、while用法

　　as表示“当……的时候”，往往和when/while通用，但它着重强调主句与从句的动作或事情同时或几乎同时发生。

　　She came up as I was cooking.(同时)

　　The runners started as the gun went off.(几乎同时)

　　when：(at or during the time that )既可以表示在某一点的时候，又可表示在某一段时间内，主句与从句的动作或事情可以同时发生也可以先后发生。

　　It was raining when we arrived.(指时间点)

　　When we were at school,we went to the library every day.(在一段时间内)

　　while意思是“当……的时候”或“在某一段时间里”。主句中的动作或事情在从句中的动作或事情的进展过程中发生，从句中的动词一般要用延续性动词。在when表示a period of time时，两者可以互换。

　　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，这里的while意思是“趁……”)

　　(2)引导时间状语从句的连接词除上述外还有：

　　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 yu 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.

　　④each time,every time,by the time

　　Each time he came to my city,he would call on me.

　　注意：表示未来情况，主句用将来时，从句用现在时。

　　2、让步状语从句

　　(1)although与though可以引导让步状语从句，不能与but连用，但可以与yet连用。

　　Although they are poor,(t)they are warm-hearted.

　　(2)even if或even though引导让步状语从句，表示“即使”，“纵然”，用来使人注意下文所强调内容的性质。

　　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等疑问词，也可以在这类疑问词后面加上ever构成whoever、whatever、wherever、however等。

　　Don't trust him,no matter what/whatever he says.

　　Whoever breaks the law will be published.

　　No matter how hard the work is,you'd better try to do it well.

　　(4)as也可以引导让步状语从句。要用倒装。

　　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、原因状语从句：because,for,as,since,now that

　　(1)表示不知道的原因时用because，即说话人认为听话人不知道，因此because从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虽然表示不知道的原因，但其语气较because要弱得多，是可说可不说的话，它只能置于主句之后，这时，for是并列连词。如果不是因果关系，而是对前面主句的内容加以解释或推断时，只能用for.如：It's morning now,for the birds are singing.(很显然，鸟叫不可能是“现在已是早上”的原因。)

　　(2)表示已经知道的原因时用as或since，即某种原因在说话人看来已经很明显，或已为听话人所熟悉，因此它是句中不很重要的部分。since要比as正式一些，它们通常被置于语句之前，但有时却相反。

　　Seeing all of the children already seated,he said，“Since everyone is here,let's start.”

　　(3)下列情况下只能使用because：

　　①在回答why的问句时;

　　②在用于强调句型时;

　　③被not所否定时。

　　4、地点状语从句：where,wherever

　　Make a mark wherever you have any questions.

　　We will go where the Party directs us.

　　5、目的状语从句：that,so that,in order that

　　注意：目的状语从句的谓语动词常与情态动词连用，否则可能是结果状语从句。不可置于句首。

　　6、结果状语从句：that,so that,so … that,such … that …

　　注意：so + 形容词/副词 + that从句;such + 名词 + that从句。

　　7、方式状语从句：as,as if(though)

　　I'll do as I am told to.

　　It looks as if it is going to rain.

　　8、比较状语从句：than,as

　　9、条件状语从句：if,unless,so (as) long as,in case,once,a far as,on condition that.

　　注意if与unless的区别：不能用and连接两个unless从句，即不能有… unless …，and unless … .但if … not and if … not却不受此限。

　　You won't lose your weight unless you eat less and unless you exercise more.(×)

　　但可以说 … unless you eat less and exercise more.

　　10、注意状语从句中从句的省略现象

　　(1)连接词 + 过去分词

　　Don't speak until spoken to.

　　Pressure can be incrased when needed.

　　Unless repaired,the washing machine is no use.

　　(2)连词 + 现在分词

　　Look out while crossing the street.

　　(3)连词 + 形容词/其他

　　常见的有it necessary、if possible、when necessary、if any等。