初三中考总复习之情态动词讲解.docx
初三中考总复习之情态动词讲解Grammar情态动词一、情态动词的语法特征：1.情态动词有一定意义，表示或暗示某种情绪或态度，表示 可能、建议、愿望、必要、允许、能力等。2.情态动词没有人 称和数的变化，即不随主语的不同而变化。3 .情态动词不能独立使用，必须和实义动词一起构成谓语。4 .情态动词+ do （不带to的不定式）。ought除外。5 .情态动词没有非谓语形式，即没有不定式、分词等形式。 二、情态动词的类型：1 .只作情态动词:can/ could; may/ might; must; ought to2 .既作情态动词又作实意动词的：need, dare。3 .既作情态动词又作助动词的：will / would ；shall/ should4 .非完全情态动词:have to； used to三、情态动词的用法：（一）can /could1 .表示能力（体力、知识、技能）。Can you lift this heavy box?（体力）Mary can speak three languages.（知识）Can you skate?（技能）此时可用be ableto代替。can只有一般现和一般过；而be ableto则有多种时态。ril not be ableto come this afternoon.当表示“经过努力才得以成功做某事”时用be ableto,不用 cano 如：He was ableto go to the party yesterday evening in spite of the heavy rain.表将来的能力及完成时态时不用can,用be ableto：The baby will be ableto walk in two weeks.She has been ableto speak English since she was very small.2 .表示推测时（具体事情有实际发生的可能性时），只用 在否定句、疑问句或感叹句中。He can't be at home now.表示某人某物一时的特点（即客观可能性）意为:有可 能，有时会时可用于肯定。Accidents can happen on such rainy days.3 .表示请求，允许，与may意思相近；Can/ May I have a look?Yes, you can./No. you can't/ No,I'm afraid not. could提出委婉的请求，（注意在回答中不用could）。Couldl have the television on?Yes, you can. / No, you can't./ No, I'm afraid not.4 .表惊异、怀疑、不理解等How can you be so rude?5 .can / could + have done在肯定句中表示“本来可以做而实 际上没做某事”；在疑问句或否定句中表示对过去行为的怀疑或不肯定，表示推测。You couldhave done better, but youdidntry your best.你本来可以做得更好，但你没努力。Hecanhave been to that town.他不可能去过那个城镇。6 . cannot help doing 禁不住cannot but do:只好； 不得不。I cannot but choose to go.cannot.enough 再怎样也不为过；I cannot help you enough.（二）may / might1.表示推测，可能性，常用于肯定和否定句中，译为“也 许"。若用于疑问句时表请求许可。It may be true.may表示推测时，表示对现在或将来要发生的事情把握不大。注意：might表示推测时，不表示时态，只是可能性比 may小。2.表示请求和允许。might比may语气更委婉，而不 是过去式。否定回答时可用can't或mustnt 表示“不可以，禁止Might/ May I smoke in this room?-Yes, you can. / Yes, please.回答时用may显得冷淡勉强 应避免用。No, you can't. / No, you mustn't. /Please don't.用MayL.?较正式和客气，而口语中多用CanI？3 .表示愿望May you be happy all your life.May you succeed!4 . might比may语气更委婉5 . might/may have done表示对过去发生的动作进行的可 能性推测。He may have gone to the clinic.他可能去医务室了。He might have read about the news in the newspaper.他可能已经从报纸上知道这个消息了。6 .may well do:完全可能；They may well win because they are the best.may as well do:最好，倒不如；You may as well do it at once.（三）must1.表示必须要做的事情，多用于义务、责任或强制命令:You must hand in your homework today.Must I / they / .?must提问，肯定回答用must,否定回答 用needn't或don't have to回答。2. mustn't表示禁止,不允许You mustn't smoke here.3 .表示建议You must go to see the film Les Miserables. Ifs wonderful.4,表示推测,只用于肯定句。否定推测用can'to mustn't 表示禁止，不允许，不表示推测！He must be reading novels now.You have worked hard all day. You must be tired.If Tom didn't leave here until five o'clock, he can*t be home yet.5 .must have done对所发生事情的肯定判断。The road is wet. It must have rained last night.He must have arrived already.其否定形式：can't/ couldn't havedone6 .有"偏偏""非得的含义：Why must it rain on Sunday?7 .比较 have to 和 must1）两词都是“必须”的意思，have to表客观的需要，must:说 话人主观看法、主观必要。My brother was very ill, so I had to call the doctor in the middleofthenight.（客观上）He said that they must work hard.（主观上）2）haveto有人称、数、时态的变化，而must只有一种形 式。He had to look after his sister yesterday.3）在否定结构中：don't have to表示"不必”（=needn而 mustn't表示禁止,不允许You don't have to tell him about it.你不必把此事告诉他。You mustn't tell him about it.你一定不要把这件事告诉他。（四）needneed既可用作情态动词，也可用作实义动词。1 .用作情态动词主要用于疑否句中。Youneedn9ttelephone him now.Need I finish the work today? 一Yes, you must. /No, you needn't / you don't have to.Idon'tthink you need worry.2 .用作实义动词时后接todo：可用于各种句式。He needs to have a rest.Youdonneed to do it yourself.We need to tell them the news.3 .实义动词 need +doing 表被动含义。want, require, worth (adj)后接doing也可表被动need doing = need to be doneYour room needs cleaning.4 . needn't have done：表示做了本不必做的事(五)will/would
