条件状语从句分为两大类

条件状语从句分为两大类 真实条件句和虚拟条件句 当 从句所表达的条件是有可能实现的 有可能是真实的条件 时 用真实条件句 如果从句所表达的条件是不可能实现 的 与客观事实完全相反的条件或假设时 用虚拟条件句 条件状语从句 由 if as so long as 和 unless 引导 条件状语从句分为两大类 真实条件句和虚拟条件句 当从句所表达的条件是有可能实现的 有可能是真实的条 件时 用真实条件句 如果从句所表达的条件是不可能实 现的 与客观事实完全相反的条件或假设时 用虚拟条件 句 真实条件句在使用中也有需要注意的事项 从句中的动 词应该用一般现在时代替一般将来时 用现在完成时代替 将来完成时 eg You can arrive in Beijing earlier for the meeting provided you don t mind taking the night train 一 混合虚拟条件句 如果条件从句的动作和主句的动作不是同时发生 主句 和从句的谓语动词的 形式应分别根据各自所表示的 时间加以调整 这种句 子叫做混合虚拟条件句 如 If he had followed my advice he would be quite all right now 从句 述说过去 主句述说现在 If China had not been liberated the working people would still be leading a miserable life 从句表示与过去的事实相反 主句说明与现在的 事实相反 二 省略 if 的倒装条件句 如果条件从句的谓语动词包含有 were 或助动词 情态 动词 had should could 有时可将连词 if 省去 而将 条件从 句的主语置于 were had should could 之后 这种用法主要用于书面语 如 Were I If I were in your place I wouldn t give it up so early 如果我是你 我不会这么早就放弃 Had I if I had known I might have joined you in the discussion 如果 之前 我知道 我会参加到你们的讨论中的 Should you If you should be interested I have a book on the subject you might like 如果你有兴趣 我有一本书 这本书有你或许喜欢的课 题 三 省略主句 只保留 if only 的条件句 虚拟条件句中的表示结果的主句有时形式上可以省略 但意义仍然存在 这 种句子只保留一个 if only 条件从句 表达说话人的强烈 愿望 如 If only she were my sister 如果她是我的妹妹就好了 四 含蓄虚拟条件句 有时虚拟条件句不用条件从句 而是通过上下文或用介 词短语等表示出来 这种句子叫做含蓄虚拟条件句 下面列举几种 1 在主语词组中表示含蓄条件 1 主语是动词不定式短语 表示含蓄条件 It would be good to leave the matter in his charge 如果 把这件事让 他负责就好了 该句可改写成 It would be good if we could leave thematter in his charge 2 主语是动名词短语表示含蓄条件 Doing the work in that way would have cost much more timeand money 如果用那种方法做这项工作就 会耗费更多的时间和金 钱 该句可改写为 If we had done the work in that way it wouldhave cost much more time and money 3 主语中带有定语从句表示含蓄条件 A man who is always thinking of others would not have donesuch a thing 如果一个人总为别人着想 他就不会做出这种事情来 4 主语中含有作定语的分词或形容词表示含蓄条件 Anyone being his position would have made no reply 任何人处在他那 个位置 都不会回答的 该句可改写为 If anyone had been in his position he wouldhave made no reply A less complicated problem would have easily been solved 如果问题 不是很复杂的话 那么就很容易 解决了 该句可改写为 If the problem had been less complicated it would have easily been solved 2 用介词短语表示含蓄条件 We could have done better under more favourableconditions 如果在更好的条件下 我们会干得更好 此句可改写为 If the conditions had been more favourable we could have done better This change could not have taken place without a solid industrial foundation 如果没有坚定的工业基础 发生这样的变化是不可能的 此句可改写为 If it had been without a solid industrial foundation this change could not hav e taken place 3 用 but 或 but for 引导含蓄条件句 but 后跟从句 but for 后跟短语 But for your help our experiment wouldn t have been sosuccessful 假如没有你们的帮助 我们的实验是不会如此成功的 But for the storm we should have arrived earlier 要不是碰到暴雨我们会到得早一些 We would have invited them to the dance but they were too busy 要不是他们太忙 我们会邀请他们来参加舞会的 此句可改写为 If they had not been so busy we would haveinvited them to the dance But that he