when,while,as,before,after,until的用法

when,while,as,before,after,until的用法 在时间状语从句(Adverbial Clause Of Time)中所表示的动作与主句所标示 的的动作关系的补充说明：

a) 同时性(Same time)A:两个同时发生的事件，不是一次性和重复性，即过去或现在的习惯 动作，连词用when,whenever eg:When he goes to town, he (always) visits his aunt. 一般现在时

She(always)felt ill when she ate oyster.(牡蛎) 一般过去时当 when 意为“每当……的时候”,相当于 whenever eg:Whenever he goes to town, he visits his aunt. ‖ When he goes to town, he visits his aunt. 同样，when /whenever 上述用法可以用 if 交替使用，表“每次，每当……” (关于这种 if- 分局的条件句详见34讲)

B. 两个同时发生的事件，如果都有延续性，而且延续时间大致相等，连词 用when,while。注：连词连接的两个分句中的动词，一定要为表示延续性动作的动词。

eg:The wind blew hard when the rain poured down.While I read, she sang. when, while前后分句都用一般过去时，有时也可前后都用过去进行体。

比较：I was cooking the dinner while he was playing the piano = I cook the dinner while he played the piano 两句句意基本相同，只不过用过去进行体更加强调事件的持续性。在一 种特殊情况下，若要强调两个事件的延续的时间正好相等，可用as long as eg:He worked as long as we played. 他工作时我们在玩

C. 两个同时发生的事件，如果都无延续性，连词用when,as soon as,just as(正当……的时候), the instant (一……就),directly (一……就), immediately 等。

eg:The dog barked when it heard a noise. She in formed her husband as soon as she arrived home. The instant I saw him, I knew he was my lost brother. She knew he wasn’t an Englishman the moment he began to speak English.

I’ll tell you directly he comes

也可以用hardly /scarcely ……when和no sooner……than等关联词表 “一……就”。 此句式一般为： 过去完成时(past perfect)+hardly / scarcely……+when+一般过去时 (simple past tense) 以及 过去完成时+no sooner……+than+一般过去时

eg:I had hardly left when the quarrel started.The doctor had scarcely go into bed when he was called out again. We had no sooner sat down than we found it was time to go.

以上三句均可用倒装词序表示

如果甲事件发生在乙事件过程中，而乙事件有延续性，甲事件无延续性或只是有 短暂延续，那么，乙事件的动词可以用进行体或者是非进行体，甲事件的动词用 非进行体，连词用while,when,as。 eg: The waiter spilt soup over me when he was serving /served me. I read a newspaper while I was waiting /waited.

有时when可以引导无限延续性事件分句，只不过不为时间状语分句而相当于 并列分句。

eg: I was cooking t

he dinner when I broke a glass = I was cooking the dinner , and at that time I broke a glass

b) 先时性(Earlier Time)和后时性(Later Time)两个连续发生事件在时间顺序上有先后之分，常用连词(或介词)有before, after, till/ until, when, since 由before和after表示甲事件先与乙事件或者后于乙事件的用法，通常可用 when表示。 eg:Before he eats ,he washes his hands. →When he has washed his hands, he eats. After he pained the windows, he pained the doors. →When he had pained the windows, he pained the doors. (这里when- 分句中用完成时态来表示动作发生先后关系。)

由于before / after 的词汇意义关系，主句和分句也可以都用一般过去时。eg:I reached the station after the train left. = I reached the station after the train had left. The train left before I reached the station . = The train had left before I reached the station.

当 When = after 时，它所引导的时间状语从句分句也用一般过去时代替 过去完成体。eg:When the teacher (had) left the room, the children started talking.