Question

when，while，as的用法区别

Answer 1

（一）、when，while都有“当……时候”的意思。when既可表示某一点时间，也可以表示某一段时间 。在when引导的时间状语从句中，其谓语动词可以是延续性的，也可以是非延续性的，可与主句中的谓语动词同时发生，也可在其后发生。 例如： 1、I was just reading a book when she came into my room. 她走进我房间时，我正在看书。 2、Were you writing when the teacher came in? 老师进来的时候，你在写信吗？ 3、When he was a child he was always trying out new ideas. 他小时候就常常试验一些新的设想。
（二）、while只能表示某一段时间，不能表示某一点时间。在while引导的时间状语从句中，其谓语动词只能是延续性的，而且也只能与主句中的谓语动词同时发生或存在。 例如： 1、While Jim was mending his bike, Lin Tao came to see him. 正当吉姆修自行车时，林涛来看他。 2、You can’t do your homework while you’re watching TV. 你不能一边看电视一边做家庭作业。
（三）、另外，when和while的区别还在于：while引导的时间状语从句多用进行时态，而when引导的时间状语从句多用一般时态。 例如： 1、While they were talking , the bell rang. 正在他们谈话的时候，上课铃响了。 2、I was doing my homework when my mother came back home yesterday evening. 昨天晚上妈妈回家的时候，我正在做家庭作

Answer 2

具体你可以参考这一段。
when，while，as引导时间状语从句的区别
when，while，as显然都可以引导时间状语从句，但用法区别非常大。
一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。
① Why do you want a new job when youve got such a good one already？（get为短暂性动词）你已经找到如此好的工作，为何还想再找新的？
②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。
③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。
④ The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。
二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。
1．从句动作在主句动作前发生，只用 when。
①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。
②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。
2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。
②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。
3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用 as。这时，as常表示“随着……”；“一边……，一边……”之意。
① As the time went on，the weather got worse．（as表示“随着……”之意）
② The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。
③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。
④The little girls sang as they went．小姑娘们一边走，一边唱。
⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。
4．在将来时从句中，常用when，且从句须用一般时代替将来时。
①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。
②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。
三、when用于表示“一……就……”的句型中（指过去的事情）。
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／ Scarcely had I closed my eyes when someone knocked at the door．我刚一闭上眼，就有人在敲门了。
②I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／Scarcely had I entered my room when the telephone rang．我刚一走进房门，电话就响了。
定语从句的关系代词 Which的用法: 若先行词指物则代替先行词在定语从句中充当主语或宾语.

This is the pen which was given by my friend.

先行词 指物代替先行词在定语从句中充当主语

This is the pen which my friend gave to me.

先行词 指物代替先行词在定语从句中充当宾语

下面是他和that在定语从句中的区别及用法：
that \which在代物时常常可以通用,但有时只宜于用which ,不用that

(1) 关系代词前有介词时.

This is the hotel in which you will stay.

(2) 如有两个定语从句,其中一句的关系代词是that,另一句宜于用which.

Let me show you the novel that I borrowed from the liberary which was newly open (新开放) to us.

注意2that \which在代物时常常可以通用,但有时只宜于用that ,不用which.

(1) 先行词是形容词最高级或者它的前面有形容词最高级时

This is the best that has been used against air pollution(反对空气污染) in cities.

English is the most difficult subject that you will learn during these years.

(2) 先行词是序数词,或它的前面有一个序数词时

He is the last person that I want to see.

(3) 主句中已有疑问词时

Which is the bike that you lost?

(4) 先行词既有人又有物时

The bike and its rider that had run over (撞倒了)an old man were taken to the police station.

(5) 先行词是all,much,little,something,everything,anything,nothing,none,the one等代词时

You should hand in all that you have.

We haven’t got much that we can offer you.

I mean the one that you talked about just now.

(6) 先行词前面有only,any,few,little,no,all,one of,the same,the very等词修饰时

The only thing that we can do is to give you some money.

Li Ming is the only one that got full marks (满分)in our class.

Li Ming is one of the students that want to be teachers in our class.

(7) 有两个定语从句,其中一个关系代词已用which,另外一个宜用that

Edison built up a factory(办了一个工厂) which produced things that had never been seen before.

定语从句的关系副词 Where的用法:若先行词指地点且其在定语从句中充当地点状语.

This is the house+I was born in the house. (=I was born there)

介词短语 副词

=This is the house where I was born.这就是我在那儿出生的房子.

先行词 关系副词

in which I was born.

介词+关系代词

which I was born in.

关系代词

这里作介宾的which和that可以省略

that I was born in

Answer 3

三者可表示“当……时候”,区别如下:
(1) 若主句表示的是一个短暂性动作,从句表示的是一个持续性动作,三者都可用:
He fell asleep when [while, as] he was reading. 他看书时睡着了。
【注】 as 用于引出一个持续性动词表示“在……期间”时,其谓语通常只能是那些含有动作(action)和发展(development)
意味的动词,一般不能是那些不用于进行时态的动词(如 be, seem, love, want, agree, see, know, have
等),所以下面一句中的 while 不能换为 as:
A:I’m going to the post office. 我要去邮局。
B:While you’re there, can you get me some stamps? 当你在邮局时,能帮我买几张邮票吗?
(2) 若主、从句表示两个同时进行的持续性动作,且强调主句表示的动作延续到从句所指的整个时间,通常要用 while:
Don’t talk while you’re eating. 吃饭时不要说话。
I kept silent while he was writing. 在他写的时候,我默不作声。
但是,若主从句表示的两个同时进行的动作含有“一边…一边”之意思,通常用 as:
She sang as she went along. 她边走边唱。
(3) 若从句是一个短暂性动作,主句是一个持续性动作,可用 as / when 但不用 while:
It was raining hard when [as] we arrived. 我们到达时正下着大雨。
(4) 若主从句表示的是两个同时(或几乎同时)发生的短暂性动作,用 as / when:
I thought of it just when [as] you opened your mouth. 就在你要说的时候,我也想到了。
(5) 若要表示两个正在发展变化的情况,相当于汉语的“随着”,一般用 as:
Things are getting better and better as time goes on. 随着时间的推移,情况越来越好。
As it grew darker, it became colder. 天色越晚,天气越冷。
(6) 表示“每当…的时候”(暗示一种规律性),一般要用 when:
It’s cold when it snows. 下雪时天冷。
He smiles when you praise him. 你夸奖他时他总是笑笑。
(7) 若主从句所表示的动作不是同时发生,而是有先后顺序时,一般要用 when:
I will go home when he comes back. 他回来时,我就回家去。
(8) when 可用作并列连词,表示“这时(突然)”;while 也可以用作并列连词,表示“而”、“却”(表示对比);但 as
则没有类似用法:
We were about to start when it began to rain. 我们正要出发,这时天开始下雨了。
He likes coffee, while she likes tea. 他喜欢咖啡,而她却喜欢茶。
(9) as 和 when 后均可直接跟一个名词,构成省略句,但 while 一般不这样用:
As [When] a boy, he lived in Japan. 他小时候在日本。
(10) when 和 while 后可接现在分词、介词短语、形容词等构成省略句,但 as 一般不这样用:
When [While] reading, he fell asleep. 他看书时睡着了。
When [While] in trouble, ask her for help. 遇到麻烦的时候你就去找她帮忙。
希望能帮助到你，望采纳！

Answer 4

as和when、while的区别

Answer 5

1. 若主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用：

He fell asleep when [while, as] he was reading. 他看书时睡着了。

　　【注】as 用于引出一个持续性动词表示“在…期间”时，其谓语通常不能是那些不用于进行时态的动词(如 be, seem, love, want, agree, see, know, have 等)，所以下面一句中的 while 不能换为 as：

A：I’m going to the post office. 我要去邮局。

B：While you’re there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗?

2. 若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用 while：

I kept silent while he was writing. 在他写的时候，我默不做声。

　　但是，若主从句表示的两个同时进行的动作含有“一边…一边…”之意思，通常用 as：

She sang as she went along. 她边走边唱。

3. 若从句是一个短暂性动作，主句是一个持续性动作，可用 as / when 但不用 while：

It was raining hard when [as] we arrived. 我们到达时正下着大雨。

4. 若主从句表示的是两个同时(或几乎同时)发生的短暂性动作，用 as / when：

I thought of it just when [as] you opened your mouth. 就在你要说的时候，我也想到了。

5. 若要表示两个正在发展变化的情况，相当于汉语的“随着”，一般用 as：

Things are getting better and better as time goes on. 随着时间的推移，情况越来越好。

As it grew darker, it became colder. 天色越晚，天气越冷。

6. 表示“每当…的时候”(暗示一种规律性)，一般要用 when：

It’s cold when it snows. 下雪时天冷。

He smiles when you praise him. 你夸奖他时他总是笑笑。
7. while 可以表示转折，“然而”。