1、IF 的虚拟语气表示说话人的主观愿望或假想，而不表示客观存在的事实。虚拟情况 从句 主句与现在事实相反 If+主语+动词过去式(be 的过去式均用were) 主语+would/should/could/might+动词原形与将来事实相反 If+主语+ should+动词原形If+主语 +were to+动词原形If+主语 + 动词的过去式主语+would/should/could/might+动词原形与过去事实相反 If+主语+ had+过去分词 主语+ would/should/could/might+have +过去分词eg.一、与现在事实相反：1、If I were you ,I sho
2、uld take an umbrella.如果我是你，我会带把伞。 （事实：我不可能是你）2、If I had one million,I would lend you some。如果我有一百万，我就会借些给你。 （事实：我没有一百万）二、与将来事实相反：1、If it should rain tomorrow,what would you do ?如果明天下雨，你怎么办？（事实：不知明天是否下雨）2、If she were to be here next Sunday,I would tell her about the matter.如果她下周日来这里的话，我就会告诉她这件事。 （事实：不知她下周日是否来）3、If there were a heavy snow next Saturday,we would make a snowman.如果下周六下大雪，我们就会去三、与过去事实相反1、If they had left earlier,we wouldnt have missed the train.如果他们早点动身的话，我们是不会错过火车的。( 事实：去晚了)2、If he had taken my advice ,he would not have made such a mistake.如果她听我的劝告的话，就不会犯这样的错误了。
