一、once作“一次”、“一遍”、“一倍”解:
1. We go to the plant once a day. 我们一天去工厂一次。
2. I did this once before, and I will do it again. 我从前做过异辞,而我现在要再作一次。
3. He read this text only once yesterday. 这个课文他昨天只读了一遍。
4. Once two is two. 一二得二。
二、once作“一度”、“曾经”解:
1. Once he learned some English. 他曾经学过一点英语。
2. I once thought that the answer to this question was correct. 我一度认为这个问题的答案是正确的。
3. There once lived an old scientist who wrote many articles. 从前有一个老科学家,他写了许多文章。
4. He remembered to have once carried out this reaction. (once说明作宾语用的不定式完成时。)他记得一度进行过这种反应。
三、once作“一旦”、“一经”解,连接时间或条件从句。例如:
1. An object, once it is in motion, will persist in that motion because of its inertia. 物体一经运动,由于惯性就将继续保持其运动。
2. Once you begin, you must continue. 一经开始,你就必须继续下去。
3. Suppose there would be no friction. Once started, a body would be kept in motion. 假设不存在摩擦。物体一经起动,就将继续保持运动。(Once引出具有条件意味的时间状语从句,省略了与主句相同的主语及其相应的be的变化。两个would表示虚拟语气。)
4. Once (it is) gone, perhaps you will never get it back. 一旦失去什么,也许你再也找不回来。(句中Once还可用When once代之,意思相同。)
四、once连接一个省略句(省略与主句相同的主语或it及其相应的be):
1. If all the impeding forces of gravitation and resistance could be removed, there is no reason why the ball, once (it is) in motion, should ever stop. 如果一切起阻止作用的引力和阻力能加以除去,就没有理由认为,球一旦处于运动中会再停下来。
2. Once combined, nitrogen is no longer chemically inert. (=Once nitrogen is combined, it is not chemically inert any longer.) 氮气一经化合,在化学上就不再是惰性气体了。
3. The magnesium has to be warmed to start a rapid reaction, but once started, large quantities of heat and light energy are liberated. (=…but once it is started, … ) 镁必须予以加热才能发生迅速反应,但反应已经开始,就有大量热和光能放出。
五、“once+过去分词”作后置定语时,可理解为“If once…”,具有条件从句含义。例如:
1. This rule once learned will never be forgotten. (=If once this rule is learned it will…)一旦学了这条规则,就永远不会忘记。
2. Such a thing once seen will always be remembered. (=If once such a thing is seen it will…) 如果见到这种事情,就将永远记住。
3. A fish once taken out of the water soon dies. 鱼从水中取出,就马上死去。
六、常用词组once(and)for all作“最后一次”、“只此一次”解以及带once的其他词组用法举例:
1. We solved once for all the difficult problem. 我们终于解决了这个难题。
2. We overthrew the rule of the landlords once and for all. 我们最后推翻了地主统治。
3. The oil worker comes to give us his lessons once in a while. 这位石油工人偶尔给我们上课。
4. Once upon a time there was a river here. 从前这里有一条河。
5. I want to search into the matter once more. 我想再次调查那件事。
6. You must settle on(或upon) a rendezvous at once. 你必须马上选定一个集合地点。
7. His talk was at once interesting and instructive. 他的讲话既有趣又有教育意义。
补充:
once引导的状语从句
once的意思是“一旦”,对于涉及once的考题,一般只要能读懂句意,弄清语境,一般不会有问题。如:
1. You will be successful in the interview ______ you have confidence. (福建卷)
A. before B. once C. until D. though
2. ______ environmental damage is done, it takes many years for the ecosystem (生态系统) to recover. (江苏卷)
A. Even if B. If only C. While D. Once
【解析】两道题都选once,均表示“一旦”。
3 You will be successful in the interview ____ you have confidence.(2007福建)
A.before B.once C.until D.though
答案:B
[解析]本题考查几个常见连词的用法。句意为:____你有了信心,你就会在面试中成功。再来看四个选项:A项before “在…之前”,“在你有信心之前,你就会在面试中成功。”显然逻辑不通;C项until“直到…才”,“直到你有了信心,你才 会在面试中成功。”也不贴切;D项though“尽管”,“尽管你有了信心,你将在面试中成功”,明显错误。因此答案为B,once意为“一旦”,句意为:一旦你有了信心,你就会在面试中成功。
once 引导时间状语从句和条件状语从句的区别:
都解释为一……就……
其实一般来讲once翻译成时间和条件都是允许的,只是哪个更贴切的不同,如
I‘ll call you once I know 翻译成我只要一知道就告诉你,比当我知道的时候我会告诉你要好一些,所以算是引导条件状语从句
而There are a lot of birds here once it is sunny翻译成当天气好的时候这就有很多鸟,就比只要天气好,这就会有很多鸟要好,算是引导时间状语从句
所以,没有绝对的对错,只有相对的更好,明白了么?
(本资源精选自网络)
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