While, since and as

1. While, since and as --Yi Gu 2013/05/15

2. While作名词 • While表示“一会儿，一段时间” e.g. Coming to another country to study requires a big adjustment and it takes a while to fit in. 来到另外一个国家学习需要适应，会花一段时间融入环境。

3. While作连词 • 引导时间状语，意义同when. e.g. While she was listening to the radio, she fell asleep. 当她正在听广播的时候，她睡着了。

4. While and when • While后面只能跟延续性动词，表示同时发生；而when后面可以跟延续性动词，也可以跟短暂性动词。在某些固定搭配后只能跟when. e.g. Be about to do something…when… was/were doing something…when… had done something…when…

5. While作连词 • While引导让步状语从句，表示“虽然，尽管”，通常放于句首。 e.g. Whiletheseexperimentsareinterestinganduseful，itisimportanttorememberthattheymaynotalwaystellusmuch. 虽然这些实验很有趣也有用，但是很重要的是要记住，这些实验也可能不会告诉你很多.

6. While作连词 • While引导条件从句，表示“只要” e.g. Whilethereislife,thereishope. 只要有生命，就会有希望。

7. TOFEL-while • During the 1940's electron microscopes routinely achieved resolution better than that with a visible light microscope, while the performance of x-ray microscopes resisted improvement. • In addition to having to be a generalist while specializing in what may seem to be a narrow field，the researcher is faced with the problem of primary materials that have little or no documentation. 1. 20世纪40年代，电子显微镜通常比可见光显微镜的分辨能力更强，而X光显微镜的表现却没有改进。 2. 除了在专攻似乎是一个狭窄领域时不得不成为多面手以外，研究人员还面临着关于原始材料的文献很少或者根本没有这一问题。

8. Since作介词 • Since后接某一特定时间点，表“自从…以后”，常与完成时连用。 e.g. He had spoken to her only once since the party. 自从那次派对以后，他只和她说过一次话。

9. Since作副词 • since表示从过去以来、以后或到现在的情形或状态，常与现在完成时态连用。 e.g. He left home two weeks ago and we haven’t heard from him since. 他两周前离开了家，到现在我们一直没有他的消息。

10. Since作连词 • Since引导原因状语从句，表示“因为，鉴于，既然”。 e.g. He didn’t come since he was busy. Since this method doesn’t work, let’s try another. 他因为忙，就没有来。 既然这个方法不管用，我们就试一下其他的方法。

11. 自从他们离开这里，我们就一直很想念他们。 自从他们离开这里，我们就一直很想念他们。 自从他们离开这里，我们就一直很想念他们。 Since作连词 • Since引导时间状语从句，从句表示的时间是“从动作或状态结束时算起”。 e.g. We have been missing them since they left here. I haven’t heard any noise since I slept. 自从他们离开这里，我们就一直很想念他们。 我醒后还未听到任何声音.

12. Since固定句型 • “It is （has been）+时间+since+过去时”，表示“自从……以来到现在已有多久。” e.g. It has been quite some time since I was lived in London. • “It was+时间+since+过去完成时”,表示“从……到过去某时间点以来” e.g. It was three years since we had been here. 我上次离开伦敦至今颇有一段时间了。 那时我们在这已呆了三年。

13. TOFEL-since • Although its influence continued throughout the mid 1920’s, it was eventually to be overtaken by a new school of thought known as Functionalism that had been present since the turn of the century. • Finally，for the many small mammals that supplement their insect diet with fruits or seeds an inability to span open gaps between tree crowns may be problematic，since trees that yield these foods can be sparse. 1. 尽管其影响在整个20世纪20年代中期继续存在，但最终还是被世纪之交以来就存在的新的思想流派——功能主义所替代。 2.最后，对于以水果或种子来补充其昆虫食物的许多小型哺乳动物而言，不能跨越树冠之间的无树问隙可能很成问题，因为生产这些食物的树林可能分布很稀疏。

14. As作副词 • 常见搭配，as…as, not as (so)…as e.g. He doesn’t speak English as/so fluently as you. 他说英文不像你那么流利。

15. As作连词 • As引导时间状语从句，和while, when同义。 e.g. I was startled as he opened the door. 当他打开门的时候，我被惊到了。

16. As作连词 • As引导原因状语从句，同because一个意思。 e.g. We must stop writing now, as I have rather a lot of work to do. 我们必须停下笔，因为我还有很多工作要做。

17. As作连词 • As引导方式状语从句，表示“正如，就像，按照”，通常搭配 just as，as if… e.g. We do farm work as the old peasant teaches us. When a pencil is partly in a glass of water, it looks as if it were broken. As(it is)in your country, we grow wheat in the north and rice in the south. 我们按照老农民教我们的方法干农活。 当我们把铅笔的一部分放进一杯水中时，它看起来就像断了一样。 正如你们国家的情况那样，我们在北方种小麦，在南方种水稻。

18. As作连词 • As引导条件状语从句，表示“只要”，常见搭配as long as. e.g. As long as you study hard, you will make great progress. 只要你用功学习，你就会进步。

19. As作连词 • as引导让步状语从句，表示“虽然，尽管”，这时从句常用倒状语序，即把从句中的表语,状语或动词原形放在as之前。 e.g. Child as she is, she knows a lot. Try as he might, Tom could not get out of the difficulties. Though she is a child, she knows a lot. 虽然她是一个小孩子，但她知道很多。 Though he might try, Tom could not get out of the difficulties. 虽然他努力过了，汤姆不能从这个困难当中脱身。

20. As作关系代词 • 引导定语从句，常见搭配 ”the same…as…; such…as…” e.g. He wished to be such a man as Linda was. He is not the same man as he used to be. 他希望能成为一个像Linda这样的人。 他已经不是以前的他了。

21. As作代词 • 引导非限制性定语从句，用来指代它前面的整个句子(即先行句)，意思是“这一点”。这个分句可以放在句首，句中，或句末。 e.g. As is well known, oceans cover more than 70% of the earth. This elephant is like a snake, as anybody can see. 众多周知，海洋覆盖了地球70%的表面。 每个人都看到了，这个大象就像一条蛇。

22. As作介词 • “如，像”：They got united as one man. • “作为，充当”：As a writer, he was famous. • 常与动词连用：regard…as/be known as/consider…as use…as/ describe…as/be remembered as /work as/ act as/be honored as/look on as…

23. As固定搭配 • As soon as: 尽快 • As well as: 表并列关系 • As well: 也，还，常放句尾 • As to: 关于，至于

24. TOFEL-as • Totally without light and subjected to intense pressures hundreds of times greater than at the Earth’s surface，the deep—ocean bottom is a hostile environment to humans，in some ways as forbidding and remote as the void of outer space. 由于完全没有光，而且承受着比在地球表面大数百倍的极大压力，深海底部对人类而言是一个充满敌意的环境，在某些方面就像外层空间一样险恶和遥远。

25. Science is built with facts just as a house is built with bricks，but a collection of facts cannot be called science any more than a pile of bricks can be called a house. 科学建立在事实上，就像房子用砖砌成一样。但收集的事实不能被叫做科学，就像一堆砖不能被称为房子一样。

26. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes. 风速随着海拔的提高而加大，这会对书造成严重的压力，高海拔地区的变形树木可以证明以上这一点。