1、IF条件状语从句条件状语从句Dacy老师老师定义定义 If 意为“如果”，引导条件状语 从句，表示假如从句的动作发 生，主句的动作就(不)会发生。If it doesnt rain,I will go to the cinema tomorrow.位置位置 从句位置灵活，可放在主句之 前，但要用逗号与主句隔开；也 可放在主句之后。My mother will take me to the park if she is free.If my mother is free,she will take me to the park.时态时态 若主句为下列情形之一，条件状若主句为下列情形之一，条件状
2、语从句要用一般现在时语从句要用一般现在时(1)当主句为一般将来时：If he comes,he will bring his violin.(2)当主句的谓语中含有 can,may,must 等情态动词时：If you lose weight,you must eat less meat.(3)当主句为祈使句时：If you are not strong enough,please dont take part in such an activity.注：助记口诀注：助记口诀 if 条件句不一般，三个要点记心间：条件句不一般，三个要点记心间：主将从现、主情从现、主主将从现、主情从现、主祈从现。
3、祈从现。时态时态 If 引导的条件状语从句引导的条件状语从句-句型转换句型转换 1.借助“祈使句+and/or+句 子”来转换(and 表顺承，or 表转折)If you study hard,you will pass the exam easily.=Study hard,and you will pass the exam easily.=Study hard,or you wont pass the exam.2.借助without或with来转换 If there is no water,fish will die.=Fish will die without water.时态时态
4、if 引导的条件状语从句引导的条件状语从句-辨析辨析 1.if 引导条件状语从句和宾语从句的区别(1)if 引导条件状语从句，表示“如 果”，从句需要遵循主将从现的原则 If it doesnt rain,I will go to the cinema tomorrow.(2)if 引导宾语从句，表示“是否”，从句不必遵循主将从现的原则 I dont know if he will come tomorrow.时态时态 2.If 与其他常见连接词的辨析与其他常见连接词的辨析(1)if 意为“如果”Difficulties are nothing if we are not afraid of
5、them.(2)unless 意为“除非；如果不”Well go there tomorrow unless it rains.(3)until/till 意为“直到”notuntil 意为“直到才”We waited until he came back.She didnt stop working until eleven o clock.(4)although/though 意为“尽管；虽然”We were not tired though/although we had worked all day.(5)since 意为“自从”或“既然”Great changes have take
6、n place in China since 1978.Since everyone is here,lets begin our meeting.趣味练习趣味练习If clauseIf+Present simplePresent simpleIf I oversleep I miss the bus.If I miss the bus,I am late for school.If I am late for school,my teacher gets angry.If clauseMain clauseIf+Present tensewill/can/may/must+verbIf I
7、go to London I will see the Big Ben.If I go to Buckingham Palace,I can take a photo of the Royal Guard.If you go to London,you must look right before crossing a streetIf clauseMain clauseIf+Past Simplewould/could/might+verbIf I were an astronaut,I would travel in a spaceship.If I travelled in a spac
8、eship,I would go to Mars.Nice to meet you!If I went to Mars,I would meet a Martian.If I didnt understand him,I would come back to the Earth.If clauseMain clauseIf+Past Perfect tensewould/could/might+have+past participleIIf you had studied hard,you wouldnt have failed your exam.IIf you had passed your exam,you could have gone to the beach.IIf I had gone to the beach,I would have made sand castles.THANK YOUDacy老师老师
