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before,after,until的区别,要写的详细点

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before,after,until的区别,要写的详细点
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例1. Larry, I can't give you an answer ____ I think it over," said joe. before ?
until?until如果用在肯定句中,则主句的动词必须是延续性动词.until是终点,指这个动作或状态一直延续到until的时间为止.
I waited until he came back 我一直等到他回来.
until 用在否定句中,主句动词是非延续性动词(换句话说,如果主句动词是非延续的就要用否定),until是起点,指这个动作在until的时间才开始
I didn't leave until he came back 直到他回来我才走
楼上I can only give you an answer until I think it over. 这个句子是错误的.
在这道题里其实并不强调“我不给你答案”这个状态的延续,而是强调在考虑之前“不能”给你答案,所以该用before,说明先想想再告诉你例2. I could not finish the homework________.
A.until he has come B.before he came
C.when he comes D.by he had comeuntil he has come 强调直到.才, 是一种临界状态
直到他回来我才完成作业
before he came 强调再他回来之前 我没法完成作业例3. But it may still be many years ( )this problem could finally be solved.
这道题选before.给的简析是“到这个问题最终解决仍然还要许多年”,例4. ___can i go out paly with.,mum?
__No, you can't ____your home work is being done.before ?
until?after是指在.之后until与TILL差不多until和till两者都可作介词、连词,一般情况下可以互换使用.用于肯定句时,主句的动词只用延续性的,它所表示的动作一直延续到till或until表示的时间为止,意为“直到……为止”;用于否定句时,主句的动词一般是非延续性的,也可以是延续性的,它所表示的动作直到till或until所表示的时间才发生,意为“直到……(才)”.如:
She watched TV until / till her mother came back.
她看电视直到她母亲回来.(看电视的动作延续到母亲回来才结束)
She didn”t watch TV until / till her mother came back.
直到她母亲回来她才(开始)看电视.(看电视的动作直到她母亲回来才发生)实际上,只要我们把握住两者使用时本身的含义及主句动词是终止性的,还是延续性的,肯定式,还是否定式两大点,就能容易地解决这类问题.现详细阐明如下:
一、在下列情况下,两者可互换用,但含义略有不同.before表示“在……之前”的意思,强调时间先后关系;而until表示“直到……才”的意思,主句是肯定句则表示主句动作的终止时间;主句是否定句则强调主句动作的起始时间.
1.主句为否定式终止性谓语动词.常见的动词是open,start,leave,arrive,finish,
stop等.例如:
(1)The noise of the street didn't stop until/before it was midnight.
(2)The children won't come back until/before it is dark.
(3)I didn't leave the lovely boy until/before his mother came home.
2.主句为肯定式、延续性谓语词,这类动词用stand,stay,talk,be,wait等.例如:
(1)He lived with his parents until/before he graduated from school.
(2)I will wait until/before he comes to my help.
(3)I shall stay heer until/before you come back.
二、在下列情况下,用before不用until.
1.主句这肯定式、终止性谓语动词,只用before.例:
(1)He fell asleep before I could take off his clothes.
(2)We arrived there before it atarted to rain.
(3)The holiday came to the end befor I knew it.
(4)He almost knocked me down before he saw me.
2.主句谓语动词强调动词的迟缓性,只用before,常伴有时间段状语或时间段暗示.例:
(1)It was quite some time before he found the elephant at all.
(2)We had walked a long way before we found some water.
(3)We had sailed for two days before we saw the land.
(4)The fire lasted about four hours before the firefighters could
countrol it.
(5)It was midnight before my brother came home.
(6)It was three months before they met again.
3.如果强调从句谓语动作未发生,就发生主句谓语动作,只用before.常译为“未及”,“不”或“不等……就”.例:
(1)We can leave early in the morning before it gets too hot.
(2)I must write it down before I forget it.
(3)We do want to buy something now before prices go up.
4.表“与其说……倒不如”,“与其……毋宁……”只用before.例:
(1)I would give up my job before I'd agree to be dismissed.
(2)He will die of hunger before he will steal.
5.在某些特定句型中用before.例如:
(1)It was not long before the whole country rose up.
(2)It will probably not be long before they understand each other.
三、下列情况一般区别用until.
1.主句是持续性谓语动词时,肯定、否定都可以,但意义完全不同.肯定表动作终止,而否定表动作开始.例如:
(1)We discussed the problem until/before he came back.我们一直讨论到他回来.
(2)We didn't discuss the problem until he came back.我们一直等到他回来后才讨论问题.
2.not…until句型尽管在某些情况下可与before互换用,但在强调句中一般仍用until.
例如:
(1)It was not until he told me that I knew it.
(2)It was not until he finished his homework that he went home.before 的用法归纳before 可以和过去完成时连接.
一. 过去完成时主要有以下几点用法:
1. 表示过去某一时间或动作之前已经发生或完成的动作或存在的状态.句中常用by, before, when, until等词引导的时间状语.它是以过去某一时间为起点,所以过去完成时是一个相对的时态,表示的是“过去的过去”.只有和过去某时间或某动作相比较时才能用到它.例如:
Most of the guests had left when he arrived at the party. 当他到达晚会时,他发现大多数客人已经离开了.
2.过去完成时还可表示过去某一时刻之前发生的动作或状态持续到过去某个时间或持续下去,常与for, since等词连用.例如:
When Jack arrived, he learned Mary had been away for almost an hour. 当杰克到时,他得知玛丽已经离开快一个小时了.
3. 用于并列句:一个并列句用的是过去式,如果另一个并列句表示的动作早于过去式这一动作,这时需用过去完成时.例如:
Tom flew home, but his father had already died.汤姆乘飞机回家,他的父亲却已经去世了.
4. 某些动词的过去完成时表示过去未实现的希望、计划或打算.常用的动词有hope, expect, suppose, think, want, wish等.例如:
They had hoped to be able to arrive before ten. 他们本来打算能在10点之前到达.
5. 在before, after, as soon as等引导的从句中,由于这些连词本身已经表示出时间先后,所以可以用过去时来代替过去完成时.例如:
二. 一般过去时和过去完成时用法有哪些不同?
1. 在主从复合句中的用法不同
(1) 用在宾语从句中
在主句谓语为一般过去时的宾语从句中,既可用一般过去时,也可用过去完成时.但两种时态的意义明显不同.试比较下列两组句子:
She said she was a doctor. 她说她是位医生.(说话时仍为医生)
She said she had been a doctor.她说她曾当过医生.(说话时已不是)
She said she had been a doctor for twenty years.她说她当过20年的医生.(主要强调说话时已当过20年医生,此状态可能已经结束,也可能还没有)
但是,如果从句中有表示具体时间的状语,则常用一般过去时.例如:
He said he was born in 1986. 他说他是 1986年出生的.
(2) 用在含有after的主从复合句中
在含有after的主从复合句中,一般在从句中使用过去完成时,主句中使用一般过去时.例如:
After he had done his homework, he went out to play football.
因连词after本身能明确表示时间的先后关系,因而多数的主句和从句均使用一般过去时.例如:
After he arrived in England, Marx worked hard to improve his English.
(3) 用在含有before的主从复合句中
用在含有before的主从复合句中,一般在从句中使用一般过去时,主句中使用过去完成时.例如:
Lily had written some letters before she went out shopping.
有时,也可以在从句中用过去完成时,主句中用一般过去时,这样就可使描述更为生动.试比较:
We got to the station before the train had left. 火车尚未开动之前,我们就到了车站.
We had got to the station before the train left. 火车开出之前,我们就已经到了车站.
像after一样, before本身就能明确地表示时间的先后关系,故多数主从句均使用一般过去时,而无需使用过去完成时.例如:
Many people left for home before the film ended.电影尚未放完,许多人就起身回家了.
(4) 用在含有when的主从复合句中
由于when本身不能明确表示时间的先后关系,故先发生的动作应用过去完成时,后发生的动作只需用一般过去时.这样用过去完成时的可能是主句,也可能是从句.例如:
When all his money had been used up, Peter had to turn to a friend for help. 当他的钱全都用光时,彼得只好转而求助于一个朋友.
有时,主句和从句的谓语动词的先后关系十分明确,两个动作紧接着发生,前一动作导致后一动作,这时两者均用一般过去时即可.例如:
When the meeting was over, we left the hall. 散会后,我们就离开了大厅.
2. 叙述几个连续的动作用法不同
在叙述两个或两个以上接连发生的动作用and, but, so或then等连接并按时间发生的先后顺序叙述时,只需用一般过去时.例如:
She entered the room, turned on the light and found everything stolen.
I lost my pen but soon found it.
She lost her pen, so I lent her mine.
但是,如果两个先后发生的动作不是按时间的顺序排列或叙述时,为明确动作发生的先后顺序,先发生的动作就得用过去完成时.例如:
The farmers were in high spirits because they had got another good harvest. 农民们兴高采烈,因为他们又获得了一次好收成.
3. 表示与过去还是现在相反的情况不同
一些表示心理活动的动词,如think, know, expect, mean, hope, want, suppose等,用一般过去时可表示存在于过去而非现在的心理活动或事与愿违的情况.例如:
I didn't know you were here. 我不知道你在这儿.
而这些词的过去完成时则表示的是过去未曾实现的愿望、打算、想法或意图等.例如:
We had hoped that you would be able to visit us. 我们原本希望你去看我们.before 的用法归纳1 作介词A.指时间.在……以前. e.g. It began to rain before midnight .B. 指位置.在……面前. e.g. They knelt before the king .C. 指顺序或排列在前面. e.g. You name comes before mine on the list .2 作连词A.在……之前. e.g. Did she leave a message before she went ?B.用于It + be +时间段 + before :在……之后才……  e.g. It willl be five years before I come back .3 常于情态动词 can / could 连用: 还没来得及……就……e.g. Before I could say a word , she had rushed out of the room . 状语丛句中before的用法一、表示“在……之后……才”.副词“才”在汉语中强调某事发生得晚或慢.如果在含有before从句的复合句中,强调从句动作发生得晚或慢时,就可以应用这种译法.二、表示“……还没来得及……就……”.目的在于强调从句动作发生之前,主句动作已发生.三、表示“在……之前就……”.这时主句与before从句中的两个动作按时间先后依次发生.四、表示“趁……”,“等到……”,或 “没等……就…… ”等.五、用于句型“It + will/would be + 时间段 + before...”句型中,表示“要过多久才…”,也可用于“It + may be + 时间段 + before...”,表示“也许要过多久才……”.其否定形式“It will/would not be +时间段+ before…”表示“不久就……,过不了多久就……”.六、用于句型 “it was +时间段+ before …” 表示 “过了(多长时间)才……”.其否定形式“ it was not +时间段+ before …” 意为“不