英语中when的用法问题

Question

请顺便回答whenever和if的同类用法

问题如下
when引导的从句中有时候用的是将来时 有时候用一般现在表将来

请问when后的时态是因什么而变化，各种变化的中文翻译因怎么翻？
和两种用法中的语境区别所在~
谢

Answer 1

[编辑本段]一、时间状语从句
要点: 时间状语从句，由以下连词引导：
when while as after before as soon as since till /until by the time 在时间状语从句中，要注意时态一致。一般情况下主句是将来时的时候，从句要用一般现在时。
1.when当。。。的时候
Mozart started writing music when he was four years old.
(当)莫扎特4岁的时候，开始写音乐作品。
2.while当。。。时
He visited a lot of places while he was traveling.
他在旅途中参观了许多地方。
3.as在。。。的同时；一边。。。一边。。。
He smiled as he stood up.
他一边站起来一边笑着。
4.after在。。。之后
He left the classroom after he had finished his homework the other day.
前几天做完作业之后回的家。
5.before 在。。。之前
Mr. Brown had worked in a bank for a year before he came here.
布朗先生来这之前已经在一家银行里工作一年了。
6.as soon as 一。。。就。。。
We began to work as soon as we got there.
我们一到那就开始工作。
I will write to you as soon as I get home.
我一到家就给你写信。
7.since 自。。。以来 到现在
表示自过去的一个起点时间到目前(说话时间)为止的一段持续时间。主句一般用现在完成时，从句用一般过去时。
Mr Green has taught in that school since he came to China three years ago.
自格林先生来中国以来，他就在这所学校教书。
(还可以用作介词，本句从句还可以用短语：since three years ago(自三年前以来)表示。)
8 till /until
都可以作连词，连接时间状语，也可以作介词，与其它词构成介词短语，在句中作状语。
They walked till /until it was dark.
他们一直走到天黑。
Xiao Ming didn’t leave home till / until his father came back.
小明直到他爸爸回来才离开家。
9. by the time 到。。。为止 (所在句子的主句应用完成时)
By the time he gets there , his father has already gone.
他到家的时候，他爸爸已经走了。
By the time I got to school, the class had already began.
我到校时，已经开始上课了。
时间状语从句（adverbial clause of time）
1.由when, while, as引导的时间状语从句。例如：
When you think you know nothing, then you begin to know something.当你以为自己一无所知的时候，你就是在开始知道一些事物了。
When truth is buried under the ground it grows, it chokes, it gathers such an explosive force that on the day it bursts out , it blows up everything with it.当真理被埋在地下的时候，它在生长，它感到压抑，它蓄存着这么一种爆炸性力量，一旦冒出，它就会炸破一切！
Strike while the iron is hot. 趁热打铁。
Will you watch my clothes while I have a swim. 我游泳的时候，请你照看一下我的衣服。
You can feel the air moving as your hand pushes through it. 当你的手在空气中挥动的时候，你就能感觉到空气在流动。
Our headmaster laughed as she spoke.我们的校长边谈边笑。
when, while和as的区别
when引导的从句的谓语动词可以是延续性的动词，又可以是瞬时动词。并且when有时表示“就在那时”。
例如：
When she came in, I stopped eating.她进来时，我在吃饭。(瞬时动词)
When I lived in the countryside, I used to carry some water for him.当我住在农村时，我常常为他担水。（延续性的动词）
We were about to leave when he came in.我们就要离开，就在那时他进来了。
While引导的从句的谓语动作必须是延续性的，并强调主句和从句的动作同时发生（或者相对应）。并且while有时还可以表示对比。例如：
While my wife was reading the newspaper, I was watching TV. (was reading是延续性的动词，was reading和was watching同时发生)
I like playing football while you like playing basketball.我喜欢踢足球，而你喜欢打篮球。（对比）
As表示“一边……一边”，as引导的动作是延续性的动作，一般用于主句和从句动作同时发生；as也可以强调“一先一后。例如：
We always sing as we walk.我们总是边走边唱。（as表示“一边……一边”）
As we was going out, it began to snow.当我们出门时，开始下雪了。（as强调句中两个动作紧接着先后发生，而不强调开始下雪的特定时间）
as when while的辨析
as when while都表示主、从句动作同时发生，三者差异如下：
表示“一边。。。一边”的意思
as 强调两个动作同时进行，并表示对比时
用于发生时间较短时
when
1、还可以表示从句动词的动作在主几句动词的动作”之前 ”或”之后”发生。
2、when＝and then; at that moment (正在那个时候)
while 1、用于时间较长时
2、 强调两个动作同时进行，并表示对比时
有时这三个连词可以互换，有时不可以。
lIt was raining hard when (as) I got there.
我到那里时，正在下大雨。 ( 动作同时发生，when可换为as, 但不能换为while，因为get是点动词.)
lWhen I had read the article, he called me.
我看完这篇文章之后，她给我打了电话。( 从句动作发生在主句之前，注意时态表达，只能用when )
lWhen I got to the cinema, the film had begun.
(当)我到了电影院时，电影已经开演了。(从句的动作发生在主句之后，只能用when,并要注意时态)
lHe was about to leave, when the telephone rang.
他正要离开，忽然电话响了。( 此时不能放在句首。主句动词一般表达 “正在” “即将”.
while, as不能代替
lShe thought I was talking about her daughter, while, in fact, I was talking about my daughter.
他以为我在谈她女儿，然而，实际上在谈论我女儿。(表转折，对比，when, as都不能代替它)
lWhile the alien was buying a souvenir, the girl called the police.
外星人买纪念品时，那女孩给警察打了电话。(表示主句，从句的动作同时发生，while后引导的状语从句的动词必须是延续动词不能是点动词，因为它表示较长时间)
lMother was worried because little Alice was ill, especially as (when/ while) father was away.
妈妈担心，因为小爱丽丝病了，特别是他父亲不在家的时候。(此时as ,when, while可通用)

Answer 2

when 英[wen] 美[wɛn]
adv. 当时; 什么时候; （用于时间的表达方式之后） 在那时; 其时;
conj. 如果; 在…时; 既然;
pron. 什么时候; 那时;
一，引导时间状语从句时，WHILE连接的是时间段，而WHEN连接的多是时间点例如What does your father do while your mother is cooking?What does your mother do when you come back?
二，WHILE可以连接两个并列的句子，而WHEN不可以例如I was trying my best to finish my work while my sister was whtching TV
三，WHEN是特殊疑问词，对时间进行提问，WHILE不是。例如，When were you bron?