狀語從句指句子用作狀語時(shí)，起副詞作用的句子。它可以修飾謂語、非謂語動(dòng)詞、定語、狀語或整個(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，位于句尾時(shí)可以不用逗號(hào)隔開。

　　讓步狀語從句

　　(1)although與though可以引導(dǎo)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(dǎo)讓步狀語從句，表示“即使”，"“縱然”，用來使人注意下文所強(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等疑問詞，也可以在這類疑問詞后面加上ever構(gòu)成whoever、whatever、wherever、however等。

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

　　Whoever breaks the law will be published.

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

　　(4)as也可以引導(dǎo)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.

　　時(shí)間狀語從句

　　(1)as、when、while

　　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 library 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……”）

　　(2)引導(dǎo)時(shí)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.

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