一、狀語(yǔ)從句的概念和類別
　　狀語(yǔ)從句指句子用作狀語(yǔ)時(shí)，起副詞作用的句子。它可以修飾謂語(yǔ)、非謂語(yǔ)動(dòng)詞、定語(yǔ)、狀語(yǔ)或整個(gè)句子。根據(jù)其作用可分為時(shí)間、地點(diǎn)、原因、條件、目的、結(jié)果、讓步、方式和比較等從句。狀語(yǔ)從句一般由連詞(從屬連詞)引導(dǎo)，也可以由詞組引起。從句位于句首或句中時(shí)通常用逗號(hào)與主句隔開(kāi)，位于句尾時(shí)可以不用逗號(hào)隔開(kāi)。
　　二、考點(diǎn)聚焦
　　1、時(shí)間狀語(yǔ)從句
　?。?）as、when、while用法
　　as表示“當(dāng)……的時(shí)候”，往往和when/ while通用，但它著重強(qiáng)調(diào)主句與從句的動(dòng)作或事情同時(shí)或幾乎同時(shí)發(fā)生。
　　She came up as I was cooking.(同時(shí))
　　The runners started as the gun went off.(幾乎同時(shí))
　　when:(at or during the time that )既可以表示在某一點(diǎn)的時(shí)候，又可表示在某一段時(shí)間內(nèi)，主句與從句的動(dòng)作或事情可以同時(shí)發(fā)生也可以先后發(fā)生。
　　It was raining when we arrived.(指時(shí)間點(diǎn))
　　When we were at school, we went to the lipary every day.(在一段時(shí)間內(nèi))
　　while意思是“當(dāng)……的時(shí)候”或“在某一段時(shí)間里”。主句中的動(dòng)作或事情在從句中的動(dòng)作或事情的進(jìn)展過(guò)程中發(fā)生，從句中的動(dòng)詞一般要用延續(xù)性動(dòng)詞。在when表示a period of time時(shí)，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……”)
　?。?）引導(dǎo)時(shí)間狀語(yǔ)從句的連接詞除上述外還有：
　?、賢ill, 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.
　?、趆ardly / 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(lái)情況，主句用將來(lái)時(shí)，從句用現(xiàn)在時(shí)。
　　2、讓步狀語(yǔ)從句
　?。?）although與though可以引導(dǎo)讓步狀語(yǔ)從句，不能與but連用，但可以與yet連用。
　　Although they are poor,(yet)they are warm-hearted.
　?。?）even if或even though引導(dǎo)讓步狀語(yǔ)從句，表示“即使”，“縱然”，用來(lái)使人注意下文所強(qiáng)調(diào)內(nèi)容的性質(zhì)。
　　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(wèn)詞，也可以在這類疑問(wèn)詞后面加上ever構(gòu)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(dǎo)讓步狀語(yǔ)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(yǔ)從句：because, for, as, since, now that
　?。?）表示不知道的原因時(shí)用because,即說(shuō)話人認(rèn)為聽(tīng)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(yǔ)氣較because要弱得多，是可說(shuō)可不說(shuō)的話，它只能置于主句之后，這時(shí)，for是并列連詞。如果不是因果關(guān)系，而是對(duì)前面主句的內(nèi)容加以解釋或推斷時(shí)，只能用for。如：It’s morning now, for the birds are singing.（很顯然，鳥(niǎo)叫不可能是“現(xiàn)在已是早上”的原因。）
　?。?）表示已經(jīng)知道的原因時(shí)用as或since,即某種原因在說(shuō)話人看來(lái)已經(jīng)很明顯，或已為聽(tīng)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(yǔ)句之前，但有時(shí)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(wèn)句時(shí)；②在用于強(qiáng)調(diào)句型時(shí)；③被not所否定時(shí)。
　　4、地點(diǎn)狀語(yǔ)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(yǔ)從句：that, so that, in order that
　　注意：目的狀語(yǔ)從句的謂語(yǔ)動(dòng)詞常與情態(tài)動(dòng)詞連用，否則可能是結(jié)果狀語(yǔ)從句。不可置于句首。
　　6、結(jié)果狀語(yǔ)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(yǔ)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(yǔ)從句：than, as
　　9、條件狀語(yǔ)從句：if, unless, so (as) long as, in case, once, a far as, on condition that.
　　注意if與unless的區(qū)別：不能用and連接兩個(gè)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(shuō) … unless you eat less and exercise more.
　　10、注意狀語(yǔ)從句中從句的省略現(xiàn)象
　?。?）連接詞 + 過(guò)去分詞
　　Don’t speak until spoken to.
　　Pressure can be increased when needed.
　　Unless repaired, the washing machine is no use.
　?。?）連詞 +　現(xiàn)在分詞
　　Look out while crossing the street.
　?。?）連詞 + 形容詞/其他
　　常見(jiàn)的有 it necessary、 if ?possible、 when necessary、 if any等。