when,while与as用法之异同

when，while与as用法之异同■崔长平河南遂平一高（463100）1.从表示的时间概念来说，这三个词的共同特点是：它们所引起的从句都可以表明主句动作发生在某一段时间或某一活动过程之中。

这时它们可以互换使用。

此时从句中的谓语动词是延续性的。

e.g. As ∕When ∕While he talked on, he got more and more excited.He was fond of swimming when ∕ while ∕as he was yet a child.（如果主句动作发生在某一时刻，即一个时间点上，这时的时间状语从句可用when或as来引导，不能使用while来引导，而且谓语动词多是非延续性的。

）e.g. When he arrived in Beijing, it happened to be raining.When he returned from work, his wife was cooking.The runners started as the gun went off.He raised his hat when he saw her.What were you doing when I called you on the phone last night.I will give it to my mother when she is back.2.就从句动作与主句动作发生的时间关系来说，when引导的从句的动作与主句的动作可以是同时或几乎同时发生的，也可以是一先一后发生的，而while和as引导的从句的动作与主句的动作一般都是同时发生的，也就是说主句动作限定在从句所表示的时间范围内。

e.g. On one occasion, when a boy, I went fishing with other boys.He turned off the light and went to bed when he finished his work.I read the book as I walked along.He was only ten when he began to work for the boss.She will take the letter to the post office when she has finished it.When the firemen got there, the fire had been put out.When she saw the mouse, she screamed.Strike while the iron is hot.Work while you work, play while you play.While ants grow, they change their form three times.Crusoe hurried home, looking behind as he went.You will grow wise as you grow older.As he looked at the note, his smile froze.3.从说话的着眼点来说，我们也可以看出这三个词的差异：when引导的从句着意于主句动作发生在某一特定时间。

e.g. When he heard the good news, he was very happy.When the boy saw the soldiers, he stopped working on the branch.另外，when含有“每当……的时候”，“在任何……的时候”之意，条件意味较浓，这时不可换为while 或 as。

e.g.It is cold when it snows.She smiles when you praise her.while引导的从句注重说明主句的动作发生在某一段时间内，同时它也侧重说明过程。

e.g.It often changes in speed and direction while it is moving.She wept while she spoke.as引导的从句强调主句与从句的行为同时发生或同时进行（伴随发生或进行）。

e.g. Tom laughed as he spoke.The clock was striking twelve as I walked down the street.As she sang, tears ran down her cheeks.4.当主句的主语和从句的主语同指一个人或事物时，三者都可以后接缩略形式。

1）when后可接：①名词或名词词组e.g.When a child, he used to go to play on the sea.②形容词e.g.If you lie upon roses when young, you will lie upon thorns when old.③介词短语e.g.When at Rome do as the Romans do.④现在分词（与句子的主语呈现逻辑上主动的主谓关系）或过去分词（与句子的主语呈现逻辑上被动的主谓关系）e.g.He gave no answer when asked what to do next.We wear plimsolls when doing physical exercises at school.When having finished his work，he went to bed and turned off the light.2）while后可接：①名词或名词词组e.g.Tom, while yet a youth, gained the prize in an international contest.②形容词e.g.He died while asleep.③介词短语e.g.While in London Lenin closely studied the English labor movement.④现在分词（用法同when）e.g.While reading, he always makes notes.His fingers trembled while doing so.3）as后一般只接名词或名词词组e.g.As a young man, he was a store keeper and later a postmaster.5.when，while，as的一些特殊用法：when①when可以表示“当某一动作将要发生、正在发生或刚刚发生，另一动作随之突然发生”。

这时when 相当于一个并列连词，位置在两分句之间。

意为and then，just at this time，and suddenly。

也有人把这种用法称为“表示突然性的when分句”。

（when之前的分句一般使用完成时、进行时和将来时，注意研究例句中时态的使用。

）e.g. An Arab was walking alone through the desert when he met two men.She just sat down for a rest, when she saw a dark shadow steal into the house.We were going to start when it rained.I was walking along the road when suddently someone patted me on the shoulder from behind. He had just finished his work when the telephone rang.They were about to leave when a little boy ran into the office.②when还可以表示“还没有……就……”，“刚刚……就……”这种意义。

这时when的位置也是处在两分句之间。

when之前的那一个分句一般含有否定意义。

e.g. I had not been there for half an hour when I heard steps outside.I had hardly opened the door when he hit me. （hardly…when…）I had scarcely come in when the phone rang. （scarcely…when…）③when从句可以用来表示条件，意义相当于if。

e.g. When the waste water from factories is made clean and used again,a lot of money is saved.while①while也可以用作并列连词，表示对比与转折。

意为“然而”，“却”，“但是”。

e.g. He observed that feathers fell to the ground slowly,while stones fell much faster.I do every bit of housework while my husband Bob just washes the dishes now and then.In some places women are expected to earn money while men work at home and raise their children.②while可以表示“尽管”，“虽然”之含义，多置于句首。

e.g. While I like the color of the hat, I do not like its shape.While I admit that the problem is difficult,I don’t think that it can’t be solved.asas引导的时间状语从句，强调主从句两动作同时发生或伴随发生。

常译作“随着……”，“一边……一边……”，“一……就……”。

e.g. He rose as she entered.We get wiser as we get older.As time went on, his theory proved to be correct.。