课件：before和since区别.ppt

可编辑 可编辑 一、 before用作连词 (3) 1． before用作连词时，意思是“在……之前；还没来得及 …… 就”。例如： Before I could say a word, she had rushed out of the room. 不等我说一句话，她就冲出了房间。 Don’t count your chickens before they are hatched. 不要高兴得过早。 before用法 2． 用于It + be + 时间段 + before...句型中，意思是“在……之后才……”。例如：  It will be five years before I come back.  我五年后才能回来。 It was not long before the enemy was driven out of their country. 不久之后，敌人就被赶走了。 如果主句中用否定式，则表示“不多久……就”。 It won’t be long before they understand each other. 他们不久就会互相了解的。  3． 还有“趁……（还没有）”之意。 例如： They are thinking of buying the house before the prices go up. 他们正在考虑趁房价未涨时把房子买下来。 Do it before you forget it. 趁早动手，以免忘了。  before long “很快，不久” 各种时态 long before “很久以前” 一般用在过去时或过去完成时 例如： ① Before long, he went to America. 不久他就去了美国。 I hope to see you before long. 我希望不久后再见到你。 ②She said she had read the novel long before. 她说她很久以前就读过这部小说。 That happened long before. 那件事发生在很久以前。 before long与long before的区别 do you know??? 一.用作介词， 意思是“从……以来， 自从”， 常与完成时连用。??? 　I haven‘t written home since Christmas　 自圣诞节以来， 我未曾写信回家。 二.用作副词，意思是“从那时以后(一直到现在)”， “其后(到现在之间)”; ever since从那以后一直 (更加强调since的用法)。 Since 的用法 Things have not changed very much since. 从那时起， 情况并没有太大的改变。 His first book was a great success and he has been famous as a writer ever since. 他的第一本书非常畅销， 从那时起他就成了一位名作家。 He got a job with the firm in 1970 and has worked there ever since. 他从1970年开始在那家公司任职， 之后就一直在那里工作。 THANK YOU SUCCESS * * 可编辑 三.用作连词 　1. 引导原因状语从句，相当于now that，意思是“因为……，既然……， 鉴于……”。 Since the rain has stopped, lets go for a walk. 既然雨停了， 我们出去散散步吧。 Since we are young， we shouldnt be too afraid of making mistakes.因为我们还年轻， 所以不应该太害怕犯错误。 2. 引导时间状语从句，此用法较复杂。 　　(1) 若since引导的状语从句的谓语动词是终止性动词(如go，come，leave， start， begin等)的过去时， 则从句表示的时间是“从该动作开始的那一时刻起”。 He has studied very hard since he came to our school. 自从来到我们学校， 他学习就非常努力。 Great changes have taken pl