unless,though,although这几个词的用法

unless,though,although这几个词的用法
unless,though,although这几个词的用法

unless,though,although这几个词的用法
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unless的用法
unless是从属连词,引导条件状语从句,含有否定意义,相当于if条件状语从句的否定形式.所以unless = if not.注意：unless引导的条件状语从句和if条件状语从句,与其它时间状语从句一样,用一般现在时代替将来时.
Unless: conj. 除非, 如果不
Unless you take more care, you’ll have an accident.
如果不多加小心的话,你会出事故的.
My baby sister never cries unless she is hungry.
我那刚出生的妹妹除非饿了,否则她是从来不哭的.
Don’t promise anything unless you’re 100 per cent sure.
不要作任何的许诺, 除非你有百分百的把握.
Unless bad weather stops me, I run every day.
除非坏天气作梗,每天我都跑步.
木头容易燃烧,除非是水湿了.
We'll be late unless we speed up.
我们要不加快些,就会迟到了.
You'll fail in English unless you work hard.
除非你努力学习,否则你英语将不及格.
You'll miss the bus unless you walk more quickly.
除非你走快一点,否则将赶不上公共汽车.
You won't hear anything unless you roll the tape ahead.
除非你把录音带往前转,否则你是不会听到任何东西的
You will never pass the exam unless you study harder.
除非你加紧学习,否则考试永远过不了关.

更详细的如下
一、unless的基本用法
连词unless意为“除非……如果不……”,“除了……”,多引导一个否定意义的真实条件句,有时也可引导非真实条件旬.unless引导条件句时,主要用于下列情况.
(1)主句为肯定句.如：
Unless I visit every bookstore in town．I shall not know whether I can get what l want．如果我不到城里每一家书店去看看,我就不知道是否能买到我想要的书.
You will miss the bus unless you hurry up．你要不快点就会错过班车.
You’ll fail in chemistry again unless you work harder．如果你不再加把劲,你化学考试还会不及格.
(2)主句为否定句.如：
Unless you oil the motor regularly．it won’t run smoothly．要不是你经常给发动机上油.它就不会转得那么顺畅.
I wouldn't be saying this unless I were sure of the facts．要是我对这些事情没有把握,我就不说这话了.
You will never get anywhere unless you have set your goal．如果你不设定目标,你哪儿也去不了.
二、应注意的一些问题
1．unless不能与if'"not换用的情况
unless在意义上相当于if...not,因此在有些场合中unless与if...not可互换使用.
如：
Unless I am mistaken．I’ve seen that man before．=lf I am not mistaken.I’ve seen that man before．如果我没搞错,我以前见过那个人.
Unless the strike has been called off,there will be no trains tomorrow．=lf the strike has not been called off.there will be no trains tomorrow．除非罢工结束了,明天才会有火车.
但在有些情况下,二者不可互换使用.如：
(1)当unless引导非真实条件句时,一般不可改用if...not.如：
They couldn’t afford to live in such an expensive apartment unless they were rich．除非他们很富有,否则就住不起这么昂贵的公寓.
They couldn’t have arrived at the site instantly unless the police had had a helicopter．除非警方有直升机,不然他们就不会即刻赶到事发地点.
以上两例中,unless从句均表示与事实相反的情况.如果把unless换成if...not(…if they were not rick,…if the police had not had a helicopter)就与原句意义完全相反了.
(2)if...not引导的条件分句可以重叠使用,unless则不可,因为unless表示唯一条
件,不能用and连接两个unless引导的从句.
如：
She won’t lose weight if she does not keep a diet and if she does not take exercise every day．=She won’t lose weight unless she keeps a diet and takes exercise every day．除非她坚持节食、每天锻炼,否则是不能减肥的.
(3)unless引导的条件句可用否定结构,而if...not引导的条件句不可再加以否定,因为两个not不能重叠使用,因此在unless引导的否定条件旬中,不能用if...not替代unless.如：
Don't ask me to explain unless you really don’t understand．除非你真不懂,不然别让我解释.
The directors have a meeting every Friday．unless there is nothing to discuss．董事会每周五开会,无事讨论除外.
You will get a good grade in the course unless you don’t do your homework．如果你(不是不)做作业的话,你就会有好的学业成绩.
(4)当if引导名词性从句时,unless不可以代替if...not,因为if=whether(“是否”).如：
It is unimportant if he will not attend the graduation ceremony．他是否参加毕业典礼无关紧要.
I doubts if he has not made a contribution to the environment．我怀疑他是不是没有为环保做过贡献.
(5)当unless作介词(“除……以外”,“除非”)时,if...not不能与其互换使用.如：
Nothing will come out of it．unless(=except)disaster．这件事除了引起灾祸之外,
不会有什么结果.
Nothing．unless a miracle,can save him．除非出现奇迹,否则他无法得救.
2．unless从句中成分的省略
unless从句的主语与主句的主语相同时,unless从句中的主语和谓语(或一部分)有时
可省略.如：
Unless(he is)in uniform.he doesn’t look like a policeman．如果不穿上制服,他看起来就不像警察.
Unless(I am)compelled t0 stay in by bad weather,I go for a walk every day．若非天气不好被迫呆在家里,我每天都出去散步.
Don't leave the building unless(you are)instructed to do so．没有得到通知,不要离开大楼.
The virus is capable of destroying an information stored in a computer unless(it is)detected and eradicated．病毒如不查出并清楚掉,会把存储在计算机里的资料全部毁掉.
3．unless从句的时态
主句是一般将来时态、祈使句或谓语中含有情态动词或主句是一般现在时,unless引导的真实条件句用一般现在时；如果强调从句动作发生在主句动作之前,从旬可用现在完成时.
Don't touch the instruments unless the teacher allows you．没有老师的允许,不要乱动仪器.
Unless you know a word,you may consult a dictionary．如果你不认识哪个词,你可以查词典.
但主句是过去将来时或过去时,unless引导的真实条件句常用一般过去时.如：
The disease prevented him from remembering things unless he was reminded by another．这种病使他记不住事,只能靠别人提醒.
4．“祈使句(肯定式)+or／otherwise+陈述句”与“unless条件句+主句”间的转换
“祈使旬(肯定式)+or(else)／otherwise+陈述句”与“unless条件句+主句”间有时可以相互转换.如：
Put on your raincoat or you’ll get soaked．=Unless you put On your raincoat,
you’ll get soaked．If you don’t put on your raincoat,you’ll get soaked．把雨衣穿上,否则你就会全身湿透的.
Store the meat in the fridge,otherwise it will go the fridge,otherwise it will go off．If you don't store the meat in the fridge,it will go off．把肉放在冰箱里,不然就会坏掉.
5．在unles引导的肯定形式的条件句中.通常用肯定词(some,already, still,too,as well等)；在if...not引导的条件句中．通常用非肯定词(any．yet．ever．either．at all等)
You ll never really know what happiness is unless you have something to compare it to．只有通过对比,才能了解幸福的含义.
1 will inform her if you haven’t spoken to her yet．如果你还没跟她说,我通知她.
不过在if…not引导的非真实条件句中,仍能用肯定词,因为这种条件句形式上是否定,意义上却是肯定.如：
If he hadn’t already prepared his lesson,he wouldn’t be allowed to go．要是他没有做完功课,是不会允许出去的.(实际已做完功课)
6．unless可用来引导出补充前言的句子
unless引导出补充前言的句子,即对刚说过的话又突然想到要补充的内容.如：
He hasn’t got any hobbies unless you call writing a hobby．他没有任何嗜好——除非把写作也算作嗜好.
Let’s play chess unless you really have something urgent to do．下盘棋吧——除非你真有急事要办.
though,although
这两个词都可以用作连词,意为“虽然”,引导一个让步状语从句.二者区别有以下几点：
（1）although 是较正式用语,语气较强,though是日常用语,比although通俗,较常用.
（2）though引导让步状语从句可用在倒置的句子里,although不可.
Child though he is , he knows a lot. 虽然他是个孩子,但却知道很多.
（3）though 可与even 和as连用,构成习语even though （即使）引导让步状语从句和as though （仿佛）引导表语从句,although则不可.
Even though I fail, I''ll keep on trying . 我纵然失败,仍会继续尝试下去.
（4）though可作副词,放在句末或插入句中.
It was hard work; I enjoyed it though. 虽苦,我却干得很快活.

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尽管，用于句首