職稱英語考試：重點語法精講
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。
【考點聚焦】
時間狀語從句
(1)as、when、while
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(fā)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(fā)生也可以先后發(fā)生。
It was raining when we arrived.（指時間點）
When we were at school, we went to the library 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(fā)生，從句中的動詞一般要用延續(xù)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：
?、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.
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 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.
