定义 由连接词if或unless引导的状语从句叫做条件状语从句。（注意：在含有条件状语从句的复合句中，如果主句是一般将来时态，从句要用一般现在是主将从先原则)在英文中，条件是指某一件事情实现之后（状语从句中的动作），其它事情（主句中的动作）才能发生，通常译作“假如，如果，除非”。 引导词： 常用引导词： if , unless 特殊引导词:aslongas（除非；只要），supposing（假设），onconditionthat（条件是），incase（如果）条件状语从句的位置可放在句首或句尾，放在句首时常用逗号与主句隔开。If引导词用法if引导的条件句有：真实条件句和非真实条件句两种:1.真实条件句：表示在某种条件下某事很可能发生。如:Ifyouaskhim,hewillhelpyou.如果你请他帮忙,他会帮你的。Ifyoufailintheexam,youwilllethimdown.如果你考试不及格,你会让他失望的。Ifitrainstomorrow,wewontgoonapicnic.如果明天下雨，我们就不去野餐。注意：在含有条件状语从句的复合句中，表示将来时态，主句是一般将来时态，从句要用一般现在时主将从现原则，并且，切记紧跟着if的那句话是从句。）2.非真实条件句是虚拟语气的一种，表示与事实相反，不可实现的条件或根本不可能存在的条件,也就是一种虚拟的条件或假设,从句多用一般过去时或过去完成时。如:IfIwereyou,Iwouldinvitehimtotheparty.如果我是你,我会邀请他参加聚会。IwouldhavearrivedmuchearlierifIhadnotbeencaughtinthetraffic.如果没有堵车,我会到的早一点儿。IfIwereyou,Iwouldgowithhim.如果我是你,我会和他一起去的。unless引导词用法固定搭配：unless=if.not除非,若不,除非在的时候Youwillfailtoarrivethereintimeunlessyoustartearlier. Ifyoudontstartearlier,youwillfailtoarrivethereintime.Unlessitrains,thegamewillbeplayed.Ifit dosentrain，thegamewillbeplayed.除非下雨,比赛将照常进行。Letsgooutforawalkunlessyouaretootired.Ifyouarenottootired,letsgooutforawalk.经典语句：Ifitdosentraintomorrow,wewillgotothezoo.条件状语从句就是用以表示“在某种条件下,会”由as(so)longas,incase引导。Solongasyourehappy,itdoesntmatterwhatyoudo.只要你高兴，你做什么都没有关系。Youmayborrowmybookaslongasyoukeepitclean.只要你保持书的清洁，你就可以把我的书借去。Takeyourumbrellaincaseitrains.带着你的伞吧，以防下雨。完成下列句子1。如果你请求他，他会帮你的Ifyou_him,he_you2。如果她早点儿起床，就有时间在家里吃早餐If she_ _alittleearlier,shellhavetimetoeatbreakfastathome.3。如果你参加聚会，你将会过得很开心。Ifyou_theparty,you_agreattime.4。如果明天下雨，我们将不去野餐Ifit_tomorrow,we_forapicnic.5。如果你经常听英文歌，你将会喜欢英语Ifyouoften_Englishsongs,you_English.单项选择1. If you _ to the party, youll have a great time. A. will go B. went C. go D. going2. It will be a long time _ Peter _ his work. A. since, has finished B. after, finishes C. when, will finish D. before, finishes.3. What will father _ us from Japan? A. take B. bring C. carry D. make 4. Weifang is famous _ kites A. for B. to C. on D. with5 I _ her the answer if she _me. A. can tell, will ask B. will tell, will ask C. would tell, ask D. will tell, asks6. What are you going to do tomorrow?-Well go to the library tomorrow if it _. A. isnt rain B. rain C. wont rain D. doesnt rain7.Do you know when he will come back tomorrow?-Sorry, I dont know. When he _ back, Ill tell you. A. comes B. will come C. come D. may come 8. What will you do if you _ to the old folks home visit?A. go B. went C. going D. will go9. If I eat _ food, Ill be very fat.A. too many B. many too C. too much D. much too10. Ill give the book to him if he _ here next Sunday.A. will come B. comes C. is coming D. came11. There _an English film in our school tomorrow.A. is going to have B. will have C. is going to be D. has12. Could you tell us where _？A. will the next Olympic Games held B. the next Olympic Games will be heldC. would the next Olympic Games be held D. the next Olympic Games would be held13. When my mother returned last night, I _ a book. A. read B. am reading C. was reading D. am going to read14. What _ you _ when it began to rain?A. do, do B. were, doing C. are, doing D. did, do15. Ill wake you up when he _back.A. will B. is going to come C. comes D. come二、用所给词的适当形式填空1. If you _(feel) tired, you _ (have) to have a rest.2. Where _ he _(see) the film if he _(have) time?3. If there _ (be) fewer trees, there _ (be) more pollution.4. He _ (dress)more casually if he _ (not work) on weekends.5. If Marcia _ (live) alone, she _ (keep) a pet parrot.6. Lana _ (buy) a new dress if the old one _ (be) out of style.7. The twins _ (fight) if they_ (argue).8. I _ (have) a bake sale if I _ (need) money for education.9. Peter _ (send) me a beautiful souvenir if he _(tour) Spain.10. If Mr. Green _ (say) I am hard- working, my parents _ (feel) glad.11. I _ (go) to the beach if it_ (not rain) this week.12. _they _ (have) a match if the P.E. teacher _ (be) busy?13. He _ (write) a letter to his grandparents if he _ (get) his report card this week.14. If she _ (get) up late, she _ (not catch) the early bus.15. Peter _ (major) in English if he _(pass) the exams in Peking University.III完成句子1.如果他到的晚了会发生什么事情？What _ if he _