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1、高考英语语法专题讲解-情态动词 情态动词：can, could, may, might,must,ought to, shall, will,would, need ,dare1. 表示推测的情态动词1.1基本原则：1.1.2 对现在或将来情况推测，用情态动词+do / be / be doing对过去的推测，用情态动词+have done / been。1.1.3表示肯定推测的情态动词,按可能性由大到小依次为:must should / ought tomaymightcould。1.1.4否定推测，按语气由强到弱依次为： cant / couldnt（根本不可能）may not might
2、 not/could not(可能不)。 1.2 具体用法：1.2.1 must be表示推测，意为“一定是” 只用于肯定句中must have done意为“一定做过某事或某事肯定发生了” 并且有前文铺垫e.g. Listen! There must be some children in the room. The road is wet. It must have rained last night.1.2.2 should (not) / ought (not) to在中表示根据常规或常识推测，表示“某事应该或不应该发生” e.g. It is nearly 7 oclock. Jac
3、k should be here at any moment. You shouldnt be texting in the class now. We are having a lesson.(should not 含有责备之意)1.2.3 can, could表达推测时，一般用于疑问句和否定句中；can用于肯定句中表示一种理论上的可能性，意为“有时候会”，并不牵涉是否真的会发生；could用于肯定句中，语气比may/ might更弱。 e.g. It is usually warm in my hometown in March, but it can be rather cold som
4、etime. 1.2.4 may (not) / might (not)表达一种不太把握的推测，意为“或许，可能”；might的语气比may较婉转。 e.g. Although this may sound like a simple task, great care is needed.2. 表达虚拟语气的情态动词 2.1 适用情况：对过去的一种结果的假设或虚拟，形式：情态动词+have done 2.2 具体用法： 2.2.1 should (not) / ought (not) to have done本（不）应该做某事，但却没有做或做了，含有责备或后悔之意。 e.g. You shou
5、ld have gone over your lesson yesterday. (In fact, you didnt go over your lesson yesterday.)2.2.2 could have done本来能够做某事但未做。 e.g. If you followed my advice, you could have finished it. 比较一下这一句： The road isnt wet. It couldnt/ cant have rained last night. (对过去的猜测)2.2.3 neednt have done: 本没有必要做某事但却做了。n
6、eednt do: 没有必要去做某事 (时间上应该是现在或将来)。 e.g. Catherine, I have cleaned the room for you.Thanks. You neednt have done it. I could manage it myself. You neednt do it. Ill do it later.2.2.4 would (not) have done:本来(不)会发生某事，但却（发生了）或没有发生。常用于虚拟条件句或含蓄虚拟条件引导的虚拟语气，表示对过去所发生事情结果的假设。 e.g. He hesitated for a moment be
7、fore kicking the ball, otherwise, he would have scored a goal.2.2.5 might have done:本来可能发生，但实际上没有发生的事。 e.g. What a pity! Considering his ability and experience, he might have done better.3.表达“情感、态度、语气”的情态动词 3.1 must: 表示主观的义务和必要,意为“必须”。用于：肯定句：You must finish it now. Yes, you must/have to.疑问句：Must I f
8、inish it now? No, you neednt/ dont. 条件句或疑问句: 可以用来表示责备、抱怨的感情色彩，意思为“偏要，硬要” e.g. May I smoke here ?If you must, choose a seat in the smoking section. John, look at the time. Must you play the piano at such a late hour?3.2 mustnt: 表示禁止 e.g. When I was young, I was told that I mustnt play with matches3.3
9、 should3.3.1表示责任和义务。e.g. According to the air traffic rules, you should switch off your mobile phone before boarding.3.3.2在虚拟条件句中用以加强假设语气，表示与将来事实相反的假设,意为“万一”。 e.g. If it should rain tomorrow, I would stay at home.万一明天下雨的Should you be fired, your health care and other benefits will not be immediately
10、 cut off.3.3.3表示说话人对某事不能理解、赶到意外，译为“竟然”。e.g. You cant imagine that a well-behaved gentleman should be so rude to a lady. 3.4 shall3.4.1用于第一和第三人称，常用于疑问句中，用来征求对方意见。 e.g Shall I carry it for you?3.4.2用于第二和第三人称，表示“命令、威胁、警告、允诺、”等。e.g Excuse me. But I want to use your computer to type a report.You shant ha
11、ve my computer if you dont take care of it .3.4.3用于宣布法律、规定的要求。e.g.What does the sign over there read? “No person shall smoke or carry a lighted cigarette，cigar or pipe in this area.” 3.5 can3.5.1表示惊异、怀疑、不相信的态度，主要用于否定句、疑问句或感叹句中。e.g. How can you say that you really understand the whole story if you ha
12、ve only covered only part of the article?3.5.2表示请求或许可。e.g. Mum, Ive been studying English since 8 oclock. Can I go out and play with Tom for a while?No, Im afraid not. Besides, its raining outside now. 3.5.3表达一般的或永久的能力。区别：be able to也可表达能力，但常用来表达在某件事情中所表现出来的能力，尤指克服困难能够完成某事。e.g. If it were not for the
13、 fact that she cant sing, I would invite her to the party. The fire spread through the hotel very quickly but everyone was able to get out. 3.6 would3.6.1 will与would3.6.1.1表示意愿: will 表示现在的意愿，would表示过去的意愿。 e.g Go where you will. If you will allow me, I will see you home. (will可用于条件句中表意愿)He wouldnt he
14、lp me yesterday. I wouldnt go. （would用于表现在的意愿时语气较委婉）3.6.1.2表示征求意见或提出请求，主要用于第二人称的疑问句中，would的语气更委婉。 e.g. Wont you take off your coat? Would Sunday night suit you? 3.6.1.3. 表示习惯和倾向性:will表示现在的习惯，would表示过去的习惯。e.g. Oil will float on water. This window wont open. When he was a child, he would often go skii
15、ng. Thats just like himhe would lose his keys! 他就是这样，老丢钥匙! (这里would表示经常发生的令人不耐烦的事)3.6.1.4. 表示推测：will用于谈论现在，would可用于谈论过去，也可用于谈论现在(语气较委婉)。e.g. Ask him. He will know. 他可能知道吧。You wouldnt know how much she loves him.你可能不知道Every family would have some sort of trouble. 家家都会有本难念的经。You will have heard of it. 你已经听到那事了吧。I thought you would ha
