while、when、as的区别为：指代不同、用法不同、侧重点不同。
一、指代不同
1、while：在…期间。
2、when：什么时候。
3、as：像…一样，如同。
二、用法不同
1、while：while用作连词时，表示“在…(过程)中，在…期间”。常用来引导时间状语从句，当主句的主语和while所引导的从句的主语一致时，while从句中的主语、谓语往往可以省去。
2、when：when的基本意思是“什么时候”。可用作疑问副词，用来询问某事曾发生或将要发生的时间，引导特殊疑问句，还可用作关系副词引导限制性定语从句、非限制性定语从句和表语从句，表示“是…时候的事”。
3、as：as用作副词时主要用来表示比较，意思是“像…一样，如同”。可以单独使用，但更多的是用在as...as结构中，其中第一个as是副词，其后可接形容词或副词。
三、侧重点不同
1、while：只能表示一段时间。
2、when：可以和延续性动词连用。
3、as：用于引出一个持续性动词。
温馨提示：答案为网友推荐，仅供参考
第1个回答 2009-05-20
while 后面接延续性行为，但这个动作肯定和主句动作时间不一样长。如：he was talking to me while he was watching the tv。应该说“看电视”比“谈话”时间长。而as通常两个动作一直相随，很可能时间相同。如：he was thinking of a question as watching the tv。这两个动作就是一直相随的。
as意为“一边……一边……”或“与……同时”，重在表示动作同时发生、伴随进行。while只指“时间段”，不指“时间点”，从句的动词只限于持续性动词。
1 从句表示"随时间推移"连词能用as，不用while。
As the day went on, the weather got worse.
日子一天天过去，天气越变越坏。
2 as引导短暂性动作的动词。
Just as I stopped my car, a man came up to me.
————————————————————————————————
when,as,while用法之异同
请看99年高考的一个选择题： <br>
－I′m going to the post office. <br>
－_____ you are there, can you buy me some stamps? <br>
A．As B．while C．Because D．If <br>
根据本题语境，选项C、D显然不合题意，故答案应在A、B之间选择。为什么正确答案为B而不是A呢？ <br>
<br>
先看when, as, while在引导时间状语从句时的主要用法： <br>
<br>
when表示“当……的时候”。从句中既可用延续性动词，又可用非延续性动词，这些动词既可以表示动作，又可表示状态。从句中的动作既可和主句的动作同时发生，又可在主句的动作之前或之后发生。如： <br>
When I came into the room, I found him lying there asleep. <br>
Mary was having dinner when I saw her. <br>
When you meet a word you don't know, consult the dictionary. <br>
She was beautiful when she was a girl. <br>
<br>
如果when从句的主语与主句主语相同，谓语又是be动词，从句主语和be可以省略：当when从句主语与主句主语相同时，用when加分词可以替代状语从句。如： <br>
When（you are）in trouble, ask her for help. <br>
When（I was）sleeping, I never heard a thing. <br>
<br>
as表示"当……时""一面……一面"，"随着"。其具体用法如下： <br>
<br>
1、表示"当……时"、"和……同时"。常指从句的动作未结束，主句中的动作就已发生。从句中多用表示动作的动词，而不用be动词或表示感觉、理解、知道这类动词。 <br>
As he stood there, he saw two men enter the bar. <br>
She dropped the glass as she stood up. <br>
As I was walking down the street, an American asked me for directions to the nearest station. <br>
<br>
2、用于平行的动作中，表示"一面……一面……"。常指一个主语同时进行两个动作。如： <br>
He sang as he worked. <br>
The students took notes as they listened. <br>
<br>
3、用于平行发展的结构中，表示"随着……"。常指一个行为是另一个行为的结果，或一种状态随另一种状态变化。句中的动词多表示状态的发展变化。 <br>
As the wind rose the noise increased. <br>
As it grew darker it became colder. <br>
As he grew older he became more confident. <br>
<br>
While表示"在……的时候"、"在……期间"。它强调主句的动作与从句的动作同时发生或主句的动作发生在从句的动作过程中。While从句中必须是表示动作或状态的延续性动词。如： <br>
Never get on or off a bus while it is in motion. <br>
The weather was fine while we were in Beijing. <br>
She called while I was out. <br>
<br>
1、如果主句的动作在从句的动作过程中发生，从句常用进行时。如： <br>
While we were swimming someone stole our clothes. <br>
Don′t talk so loud while others are working. <br>
<br>
2、如果主句和从句主语相同，while加现在分词可代替状语从句。如： <br>
We must strike while the iron is hot. <br>
He took a bath while I was preparing dinner. <br>
Come and pay a visit to the park while the flowers are in bloom. <br>
<br>
通过以上分析我们可以看出，when, as, while引导时间状语从句时，侧重点有所不同。 <br>
1、When可指时间点，又可指时间段，从句中可用延续性动词，也可用非延续性动词。 <br>
2、While总是指一个时间段，从句中必须用延续性动词。 <br>
3、as多用于平行结构。表示两个动作同时发生：一个主语同时进行两个动作：一种状态随另一种状态的变化而变化。 <br>
4、表示主句的动作发生在从句的较长动作过程中，when, while, as均可使用。从句中为be动词时，多用when和while。谈论两个同时进行的长动作可用while；谈论两个平行动作或两种状态变化多用as。 <br>
<br>
<br>
再看文章开头所给的高考题，主句动词为buy，从句动词为be，不是两个平行动作，显然不应选项A，所以最佳答案为B。
as意为“一边……一边……”或“与……同时”，重在表示动作同时发生、伴随进行。while只指“时间段”，不指“时间点”，从句的动词只限于持续性动词。
1 从句表示"随时间推移"连词能用as，不用while。
As the day went on, the weather got worse.
日子一天天过去，天气越变越坏。
2 as引导短暂性动作的动词。
Just as I stopped my car, a man came up to me.
————————————————————————————————
when,as,while用法之异同
请看99年高考的一个选择题： <br>
－I′m going to the post office. <br>
－_____ you are there, can you buy me some stamps? <br>
A．As B．while C．Because D．If <br>
根据本题语境，选项C、D显然不合题意，故答案应在A、B之间选择。为什么正确答案为B而不是A呢？ <br>
<br>
先看when, as, while在引导时间状语从句时的主要用法： <br>
<br>
when表示“当……的时候”。从句中既可用延续性动词，又可用非延续性动词，这些动词既可以表示动作，又可表示状态。从句中的动作既可和主句的动作同时发生，又可在主句的动作之前或之后发生。如： <br>
When I came into the room, I found him lying there asleep. <br>
Mary was having dinner when I saw her. <br>
When you meet a word you don't know, consult the dictionary. <br>
She was beautiful when she was a girl. <br>
<br>
如果when从句的主语与主句主语相同，谓语又是be动词，从句主语和be可以省略：当when从句主语与主句主语相同时，用when加分词可以替代状语从句。如： <br>
When（you are）in trouble, ask her for help. <br>
When（I was）sleeping, I never heard a thing. <br>
<br>
as表示"当……时""一面……一面"，"随着"。其具体用法如下： <br>
<br>
1、表示"当……时"、"和……同时"。常指从句的动作未结束，主句中的动作就已发生。从句中多用表示动作的动词，而不用be动词或表示感觉、理解、知道这类动词。 <br>
As he stood there, he saw two men enter the bar. <br>
She dropped the glass as she stood up. <br>
As I was walking down the street, an American asked me for directions to the nearest station. <br>
<br>
2、用于平行的动作中，表示"一面……一面……"。常指一个主语同时进行两个动作。如： <br>
He sang as he worked. <br>
The students took notes as they listened. <br>
<br>
3、用于平行发展的结构中，表示"随着……"。常指一个行为是另一个行为的结果，或一种状态随另一种状态变化。句中的动词多表示状态的发展变化。 <br>
As the wind rose the noise increased. <br>
As it grew darker it became colder. <br>
As he grew older he became more confident. <br>
<br>
While表示"在……的时候"、"在……期间"。它强调主句的动作与从句的动作同时发生或主句的动作发生在从句的动作过程中。While从句中必须是表示动作或状态的延续性动词。如： <br>
Never get on or off a bus while it is in motion. <br>
The weather was fine while we were in Beijing. <br>
She called while I was out. <br>
<br>
1、如果主句的动作在从句的动作过程中发生，从句常用进行时。如： <br>
While we were swimming someone stole our clothes. <br>
Don′t talk so loud while others are working. <br>
<br>
2、如果主句和从句主语相同，while加现在分词可代替状语从句。如： <br>
We must strike while the iron is hot. <br>
He took a bath while I was preparing dinner. <br>
Come and pay a visit to the park while the flowers are in bloom. <br>
<br>
通过以上分析我们可以看出，when, as, while引导时间状语从句时，侧重点有所不同。 <br>
1、When可指时间点，又可指时间段，从句中可用延续性动词，也可用非延续性动词。 <br>
2、While总是指一个时间段，从句中必须用延续性动词。 <br>
3、as多用于平行结构。表示两个动作同时发生：一个主语同时进行两个动作：一种状态随另一种状态的变化而变化。 <br>
4、表示主句的动作发生在从句的较长动作过程中，when, while, as均可使用。从句中为be动词时，多用when和while。谈论两个同时进行的长动作可用while；谈论两个平行动作或两种状态变化多用as。 <br>
<br>
<br>
再看文章开头所给的高考题，主句动词为buy，从句动词为be，不是两个平行动作，显然不应选项A，所以最佳答案为B。
第2个回答 推荐于2017-10-01
while与when以及as之间的区别：
1. 当从句中的谓语动词是持续性的动作时,我们可以用while, when或as。
While / When / As I was walking down the
street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车。
2. 当从句中的谓语动词表示瞬间动作时,不可用while。
He was on the point of leaving when
someone knocked at the door. 他正要走,这时有人敲门。
3. 如果谈论两个长动作,最常用的是while。
While John was sitting biting his nails,
I was working out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。
不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。
As we talked on, he got more and more
excited. 我们继续往下谈的时候,他越来越兴奋。
4. 如果表示两个短动作或事件同时发生,最常用的是as或just as,或when。
Just as he caught the ball, there was a
tearing sound. 当他抓住球的时候,有一种撕裂的声音。
I thought of it just when you opened your
mouth. 就在你要说话的时候,我也想到了。
1. 当从句中的谓语动词是持续性的动作时,我们可以用while, when或as。
While / When / As I was walking down the
street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车。
2. 当从句中的谓语动词表示瞬间动作时,不可用while。
He was on the point of leaving when
someone knocked at the door. 他正要走,这时有人敲门。
3. 如果谈论两个长动作,最常用的是while。
While John was sitting biting his nails,
I was working out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。
不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。
As we talked on, he got more and more
excited. 我们继续往下谈的时候,他越来越兴奋。
4. 如果表示两个短动作或事件同时发生,最常用的是as或just as,或when。
Just as he caught the ball, there was a
tearing sound. 当他抓住球的时候,有一种撕裂的声音。
I thought of it just when you opened your
mouth. 就在你要说话的时候,我也想到了。
第3个回答 2019-04-12
as,
when,
while的区别
as,
when,
while都表示主、从句的动作或状态同时发生，但三者意义不尽相同。as和when引导的从句既可表示一点时间，也可表示一段时间，从句中的谓语动词既可以是持续性动词，也可以为短暂性动词，经常可以互换使用；while引导的从句通常表示一段时间，从句中宜用持续性动词作谓语。当从句中的谓语动词为持续性动词时，这三者可以通用（前面例句中已有体现），再如：
Mother
was
worried
because
little
Alice
was
ill,
especially
as
/
when
/
while
father
was
away
in
France.妈妈担心，因为小艾丽思病了，特别是当父亲远在法国的时候。
如果从句和主句要表示一个人的两个动作交替进行或同时完成时，则多用as，可译为“一边......，一边......”。例如：
He
looked
behind
from
to
time
as
he
went.他一边走，一边不时地往后看。
As
time
goes
on,
it’s
getting
warmer
and
warmer..随着时间的推移，天气变得越来越暖了。
I
thought
of
it
just
as
you
opened
your
mouth.你一张嘴我就知道你要说什么。（若表示两个短促动作几乎同时发生时，用as的场合多于when.）
当主从句之间表示转折或对比关系时，多用while,
不用as或when。如：
She
thought
I
was
talking
about
her
daughter,
while
in
fact,
I
was
talking
about
my
daughter.她以为我在谈论她女儿，而事实上，我在谈论我的女儿。
如果表示从句的动作在主句的动作“之前”或“之后”发生时，多用when（=after）,
不用as或
while。此外，when还含有“at
that
moment”的意思（=
and
then），引起的句子不能放在句首，也不能用as,
while来替换。例如：
He
was
about
to
leave
when
the
telephone
rang.他正要离开，忽然电话铃响了。
We
were
watching
TV
when
suddenly
the
lights
went
out.我们正在看电视，突然灯灭了。
They
had
just
arrived
home
when
it
began
to
rain.他们刚到家，天就开始下雨了。
when,
while的区别
as,
when,
while都表示主、从句的动作或状态同时发生，但三者意义不尽相同。as和when引导的从句既可表示一点时间，也可表示一段时间，从句中的谓语动词既可以是持续性动词，也可以为短暂性动词，经常可以互换使用；while引导的从句通常表示一段时间，从句中宜用持续性动词作谓语。当从句中的谓语动词为持续性动词时，这三者可以通用（前面例句中已有体现），再如：
Mother
was
worried
because
little
Alice
was
ill,
especially
as
/
when
/
while
father
was
away
in
France.妈妈担心，因为小艾丽思病了，特别是当父亲远在法国的时候。
如果从句和主句要表示一个人的两个动作交替进行或同时完成时，则多用as，可译为“一边......，一边......”。例如：
He
looked
behind
from
to
time
as
he
went.他一边走，一边不时地往后看。
As
time
goes
on,
it’s
getting
warmer
and
warmer..随着时间的推移，天气变得越来越暖了。
I
thought
of
it
just
as
you
opened
your
mouth.你一张嘴我就知道你要说什么。（若表示两个短促动作几乎同时发生时，用as的场合多于when.）
当主从句之间表示转折或对比关系时，多用while,
不用as或when。如：
She
thought
I
was
talking
about
her
daughter,
while
in
fact,
I
was
talking
about
my
daughter.她以为我在谈论她女儿，而事实上，我在谈论我的女儿。
如果表示从句的动作在主句的动作“之前”或“之后”发生时，多用when（=after）,
不用as或
while。此外，when还含有“at
that
moment”的意思（=
and
then），引起的句子不能放在句首，也不能用as,
while来替换。例如：
He
was
about
to
leave
when
the
telephone
rang.他正要离开，忽然电话铃响了。
We
were
watching
TV
when
suddenly
the
lights
went
out.我们正在看电视，突然灯灭了。
They
had
just
arrived
home
when
it
began
to
rain.他们刚到家，天就开始下雨了。
第4个回答 2009-05-10
1. 当从句中的谓语动词是持续性的动作时,我们可以用while, when或as。
While / When / As I was walking down the street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车。
2. 当从句中的谓语动词表示瞬间动作时,不可用while。
He was on the point of leaving when someone knocked at the door. 他正要走,这时有人敲门。
3. 如果谈论两个长动作,最常用的是while。
While John was sitting biting his nails, I was working out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。
不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。
As we talked on, he got more and more excited. 我们继续往下谈的时候,他越来越兴奋。
4. 如果表示两个短动作或事件同时发生,最常用的是as或just as,也可用when。
Just as he caught the ball, there was a tearing sound. 当他抓住球的时候,有一种撕裂的声音。
I thought of it just when you opened your mouth. 就在你要说话的时候,我也想到了。
While / When / As I was walking down the street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警车。
2. 当从句中的谓语动词表示瞬间动作时,不可用while。
He was on the point of leaving when someone knocked at the door. 他正要走,这时有人敲门。
3. 如果谈论两个长动作,最常用的是while。
While John was sitting biting his nails, I was working out a plan to get us home. 约翰坐在那里咬指甲时,我想出了一个回家的办法。
不过, as是可以用来说明两种正在发展或变化的情况的,这时as引导一个持续性的动作,主句中的动作与之同时进行。
As we talked on, he got more and more excited. 我们继续往下谈的时候,他越来越兴奋。
4. 如果表示两个短动作或事件同时发生,最常用的是as或just as,也可用when。
Just as he caught the ball, there was a tearing sound. 当他抓住球的时候,有一种撕裂的声音。
I thought of it just when you opened your mouth. 就在你要说话的时候,我也想到了。