[图文]高中英语语法if条件句If - Clauses.ppt

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1、IFClausesTo express a consequence depending on a condition,we use the conditional,which consists of an IF clause.The IF clause can precede or follow the main clause.When the IF clause comes first,a comma is placed between the two clauses.If clause(condition)Main clause(consequence)Ifyoubookyourholid

2、ayinadvance,yougetadiscount.Depending on the level of probability(certain,probable,possible or purely theoretical conditions)different tenses are used in two parts of the conditional.There are four types of conditional:type zero,one,two and three,which we are going to explain.TYPEZEROIn the IF claus

3、e of the zero conditional,we describe a consequence that takes place regularly and with certainty.If clause:if+present simpleMain clause:present simpleIfIdrinkcoffeeintheevening,Icantgothesleep.If clause:if+present simpleMain clause:present simpleIfunemploymentisrising,peopletendtostayintheirpresent

4、jobs.If clause:if+present simpleMain clause:present simpleIfyouvisitLondon,goontheLondonEye.The zero conditional is used to:express general truths,scientific and mathematical laws,technical procedures,instructions.Thedaysgetlongerifyoutravelnorth.Ifyoupressthiskey,thedisplaylightsup.give advice.In t

5、his case,the present form of imperative or modal(can or may)is used in the main clauseGo/Youcangotobedifyoufeeltired.TYPEONEIn the first conditional,we describe a real possibility.We talk about facts that,given certain conditions,probably or possibly will take place in the future.In this case,the ve

6、rb tenses are usually:If clause:if+present simpleMain clause:will/ll/wont+base formIfitdoesntrain,wellhaveabarbecueinthegardentomorrow.IfIfindheraddress,Iwillsendheraninvitation.IfIdontseehimthisafternoon,Iwillphonehimintheevening.NOTE:In the IF clause it is possible to use either the present simple

7、 or the present continuous.Ifyoucometomyhouse,Illshowyoumypaintings.If you are staying overnight,Ill try to find you a room.In the main clause,the use of will indicates a certain consequence.To indicate that something is possible,we use modal can,while for an uncertain consequence we use the modal m

8、ay.If you spend too much time in the sun,you may get sunburnt.(it isnt certain)TYPETWO When we assume a condition to be improbable or imaginary and that we dont expect to happenbut is however,theoretically possible,we can use the second conditional.IfIwonamilliondollarsonthelottery,Iwouldstopworking

9、andwouldgoandliveintheCaribbean.(itishighlyunlikelybutishoweverpossible)The second conditional is also used when propose a different situation to the present reality.If you worked harder,your grades would be much better.(situationthatisdifferenttothepresentreality:atthemomentyouarentworkinghardenoug

10、h)The structure of the second conditional is:If clause:if+past simpleMain clause:would/d/wouldnt+base formIfIhadmyowncar,Iwoulddrivetowork.IfIfoundheraddress,Iwouldsendheraninvitation.IfIhadalotofmoney,Iwouldntstayhere.Note how the second conditional is structured in the question form:Ifyouwonsomebi

11、gmoney,wouldyouspenditallorwouldyousavepartofit?When the verb be is present in an if clause,were is used for all persons.In spoken English,was is also used for the first and third person singular:If I/he/she/it were.was.Hewouldmakeaverygoodcareerifhewas/werealittlemoreambitious.The expressions If i

12、were you/him/her.is used to give advice and warnings.IfIwereyou,Idtalktoher.In a main clauses,as an alternative to would,other modals can be found such as:could to express ability or possibility,might to express uncertainty and should to express a piece of advice.Ifyouplayedamusicalinstrument,youcou

13、ldjointhelocalbend.IfshetriedJapanesefood,shemightfindthatshelikesit.IfIshouldwintherace,Ishouldthankthecoachforhishelp.The modals would,should or could are often found in if clauses.Would is used in if clauses to express a request in a polite and formal way,or even to expresswillingness to do somet

14、hing.Ifyouwouldkindlytellthemanager,Iwouldreallybegrateful.The use of should in if clauses makes the hypothesis more impropable.Ifitshouldhail,theharvestwouldbelost.The use of could in if clauses indicates the ability and possibility.Ifyoucoulddance,youwouldhavealotmorefun.TYPETHREEWhen we propose a

15、n impossible condition,because it refers to the past and it is therefore nolonger possible,we use the third conditional.Ifyouhadaskedme,Iwouldhavehelpedyou.IfIhadfoundheraddress,Iwouldhavesentheraninvitation.IfJohnhadhadthemoney,hewouldhaveboughtaFerrari.(Sometime in the past,I wanted to send an inv

16、itation to a friend.I didnt find her address,however.So in the end I didnt send her an invitation.)(I knew John very well and I know that he never had much money,but he loved Ferraris.He would have loved to own a Ferrari,but he never had the money to buy one.)The structure of the third conditional i

17、s:If clause:if+past perfect(had/d/hadnt+past participle)Main clause:would/d/wouldnt have+past participleIfyouhadcometotheconcertwithus,Youwouldcertainlyhaveenjoyedit.IfIhadseenyou,ofcourseIwouldhavesaidhello.IfIhadntbeensotired,Iwouldhavegoneout.The other modals might,should or could can also been f

18、ound in the third conditional.Youmighthavesucceededifyouhadtriedhardenough.IfIhadtakenmyracketwithme,Icouldhaveplayedtenniswithyou.Now,lets take a look at the summary of the different types of conditional in the table:If ClauseMain clauseExplanationType 0Ifyoustudyhard,yougetgoodresults.Consequencet

19、hatisalwaystrueingeneral.Type 1Ifyoustudyhard,youwillgetgoodresults.also:youmaygetgoodresultsCertainresultinyourparticularcase.Type 2Ifyoustudiedhard,youwouldgetgoodresults.also:youcouldget/youmightgetgoodresults.Possibleconsequences,givenaconditiondifferentfromthepresentrealityorfacts.Type 3Ifyouhadstudiedhard,youwouldhavegotgoodresults.also:youcouldhavegot/mighthavegotgoodresults.Impossibleconditionbecauserefferedtothepast.THANKYOUFORYOURATTENTION!