If-If-条件句的用法条件句的用法1 1条件句n条件句（条件句（conditional）是由）是由 条件状语条件状语分句（分句（if 分句）分句） + 主句主句 构成的复杂构成的复杂句句(complex sentence)。n一共分为三种一共分为三种(3 types)1 if whenever(the meaning is close to)2 主将状从现主将状从现 3虚拟虚拟真实条件句真实条件句非真实条件句非真实条件句 The type 1 : ifwhenevernType 1 是真实条件句（是真实条件句（Real Conditional）的一种。在这）的一种。在这种条件句中，种条件句中，if 的意义接近于的意义接近于whenever，所以这种句型，所以这种句型又被称为又被称为“whenever-型型”，可用于，可用于3种种 场合：场合：n1、表示普遍真理和客观事实、表示普遍真理和客观事实 （tell the truth)nFor example:n If you pour oil on water, it floats.n If the temperature drops to 0 degrees Centigrade, water freezes.n总结：由上两例可看出，凡表示不受时间限制的自然法则总结：由上两例可看出，凡表示不受时间限制的自然法则的条件句，其的条件句，其 if-分句和主句的谓语动词都用分句和主句的谓语动词都用一般现在时一般现在时 ：nPattern：（：（if) simple present +(Main) simple presentn2、表示现在习惯动作、表示现在习惯动作nFor example: n If it rains, I go to work by bus.nIf I make a promise, I keep it .n总结：在上述表示现在习惯动作的条件句中，总结：在上述表示现在习惯动作的条件句中， if-分句和主句的谓语分句和主句的谓语动词也都是用动词也都是用一般现在时一般现在时：nPattern： （if) simple present +(Main) simple presentn3、表示过去的习惯动作、表示过去的习惯动作nFor example:nIf I was hungry, I usually had a full meal.总结：表示过去习惯动作的条件句中，总结：表示过去习惯动作的条件句中，If-分句和主句的谓语动词都用分句和主句的谓语动词都用一般过去时一般过去时。Pattern ：（：（if）simple past + （Main ) simple past.The type 2 : 主将状从现nType 2 是真实条件句的主体，最普遍最常用。（是重点）是真实条件句的主体，最普遍最常用。（是重点）n一、基本形式：一、基本形式：(2种）种）n1、if-分句用一般现在时表示将来时间，主句用分句用一般现在时表示将来时间，主句用shall / will / can / may (现在时）现在时）nPattern :（if）simple present + （Main）shall / will，etc 例句：例句： If I see him again, I will tell him what you said. What will happen if they cant reach an agreement? If you set your alarm clock , you wont be late tomorrow.n2、if 分句分句 用一般现在时表示将来时间，主句用动词祈使式：用一般现在时表示将来时间，主句用动词祈使式：nPattern : （If）simple present + （Main）imperativen例句：例句：n If you wake up before me, give me a call .n If you go out this room, turn off the lights. 二、变体形式（二、变体形式（3种）种）n1、if-分句动词不管主语的人称和数如何，一律用分句动词不管主语的人称和数如何，一律用should+不定式，不定式，主句动词可根据语义意图采用不同形式。主句动词可根据语义意图采用不同形式。nExample ：n If it should rain again, the flowers will bloom.n If you should come tomorrow, I would tell you the truth.n说明：在这里，说明：在这里，should 仅表示一种不太肯定的婉转口气，并不影响仅表示一种不太肯定的婉转口气，并不影响条件的真实性。条件的真实性。n2、在、在if-分句中用分句中用“will+不定式不定式”并不单纯表示将来意义，这里的并不单纯表示将来意义，这里的will是个表示是个表示“意愿意愿”的情态助动词的情态助动词 = be willing to example : If you will reserve seats , we shall be sure of a comfortable journey.3、用、用 would 还是表示还是表示“意愿意愿”，常用于，常用于 客气的请求，这时，主语动客气的请求，这时，主语动词既可用词既可用will/shall +inf. 也可用也可用would /should / could/ might +inf.Example : If you would try Italian food , you would like it.注意：注意： 省略了省略了 towilling to reserve 虚拟（第三条件句第四条件句）n这种是非真实条件句（这种是非真实条件句（unreal conditional) 的一的一种。所谓种。所谓“非真实条件非真实条件”，在语义上包含着不同，在语义上包含着不同程度的程度的“非真实性非真实性”。这种类型的条件句也可分。这种类型的条件句也可分为基本形式和变体形式。为基本形式和变体形式。虚拟基本类型基本类型（if）simple past / were + (main) would (could ,might,etc) +inf例如例如 If we caught the 10 oclock train, we would (could,might,ect)get there by lunch-time.主句动词都用主句动词都用would could might ,etc 不定式。但不定式。但可能性的程度不一样可能性的程度不一样If I knew how it worked, I could tell you what to do .(条件与现实相反，根本不可能告诉对方做什么）条件与现实相反，根本不可能告诉对方做什么）虚拟n这种句型的动词形式还可根据语义意图采用进行这种句型的动词形式还可根据语义意图采用进行体形式。体形式。nIf we were on holiday now , we d be having a wonderful time虚拟变体形式变体形式 (If) were to +inf+(main)would,etc+inf例：例： If our train were to arrive punctually, we should have time to visit your sister.要注意表示非真实条件的要注意表示非真实条件的were to 与表示与表示“义务义务”（obligation） 的的am / is / are to 和和was/ were to 的区别的区别虚拟If he were to get in touch with me , I could explain. = Supposing he got in touch with me.(非真实条件）非真实条件）If he was to get in touch with me , why hasnt he done so ?= If the arrangement was that he should get in touch with me , why.? (表示表示“义务义务”）里一个变体是在里一个变体是在if-分句中用分句中用would + 不定式不定式 表示不大可能表示不大可能实现的实现的意愿意愿If you d cook the dinner , id do the washingup afterwards.（省略（省略 to)虚拟n(If) had + -ed 分词分词 +Main would (could might,ect) have-ed分词分词n例如例如nIf we had caought the 10 oclock train ,we would have got there by lunch-time.nWe would /could /might have called you if we had known your telephone number虚拟n如果句子的前半段如果句子的前半段 （if -分句）分句） 是表现现在不是表现现在不大可能实现的条件，而后半段（主句）却表示与大可能实现的条件，而后半段（主句）却表示与过去事实相反的情况，前后在逻辑意义上不相协过去事实相反的情况，前后在逻辑意义上不相协调。但在保证句子合乎逻辑的前提下，也可根据调。但在保证句子合乎逻辑的前提下，也可根据语义意图混合实用俩种句型的动词形式语义意图混合实用俩种句型的动词形式nIf he had wanted to dance ,Id have taken him to discotheque(迪斯科舞厅）迪斯科舞厅）虚拟n第四条件句的变体形式第四条件句的变体形式n（If）were to have + -ed 分词分词 +Main would (could, might, ect)have -ed 分词分词 n例如例如n If you were to have asked me , I would have been only too willing to help.虚拟30分分20分分40 分分10 分分10分题nI used to walk to work.But if it _(rain), I went by bus. rained20分题nIf you move to your left, you _(be)able to see the churchwill be30分题nHe could repair the roof himself if he _(have) a long ladder. had40分题If the story hadnt been ture, the newspaper _(not print) it . wouldnt have printedif i were a boy beyoncenIf I were a boy nEven just for a day nId roll outta bed in the morning nAnd throw on what I wanted then go nDrink beer with the guys nAnd chase after girls nId kick it with who I wated nAnd Id never get confronted for it. nCause theyd stick up for me. nIf I were a boy nI think I could understand nHow it feels to love a girl nI swear Id be a better man. nId listen to her nCause I know how it hurts nWhen you lose the one you wanted nCause hes taken you for granted nAnd everything you had got destroyed nIf I were a boy nI would turn off my phone nTell evveryone its broken nSo theyd think that I was sleepin alone nId put myself first nAnd make the rules as I go nCause I know that shed be faithful nWaitin for me to come home (to come home) nIts a little too late for you to come back nSay its just a mistake nThink Id forgive you like that nIf you thought I would wait for you nYou thought wrong nBut youre just a boy nYou dont understand nYeah you dont understand nHow it feels to love a girl someday nYou wish you were a better man nYou dont listen to her nYou dont care how it hurts nUntil you lose the one you wanted nCause youve taken her for granted nAnd everything you have got destroyed nBut youre just a boy结束结束