情态动词的基本用法

情态动词的基本用法

情态动词有：can (could), may (might), must, have to, shall (should), will (would), need, dare (dared), ought to. 情态动词无人称和数的变化,不能独立使用,它与其后面的动词原形合成谓语.情态动词的具体用法如下： 一、can, couldcan 的用法1. 表能力.如： A computer can not think for itself, it must be told what to do.2. 表可能性.如： — Will you stay for lunch? __ Sorry, I can't. My btother is coming to see me.3. 表推测,意为“可能”、“或许”,用于疑问句或否定句中. can't 后用一般式表示对现在情况的推测,用完成式表示对过去情况的推测.例如： Susan can't have written a report like this.could 的用法1. can 的过去式.例如：I could speak a little Japanese when I was at college but now I have forgotten all of them except a few words.2. 客气的请求.例如：Could I borrow your dictionary?3. “could +have +过去分词”表示对过去能做而未做的事感到惋惜、遗憾.例如：—I stayed at a hotel while in New York.__ Oh, did you? You could have stayed with Barbara.4.“ couldn't +have + 过去分词”表示对过去情况的推测,意思是“不可能”.例如： He could not have seen the film because he knew nothing about it. 二、 can , be able to 的区别can 和be able to 在表示“能力”时意思相同,但在用法上有区别.1. can 表示主观能力, be able to 表示客观能力. I can drive , but I'm not able to drive now because I'm drunk.2. can 只有现在式和过去式,而 be able to 可用各种时态.3. be able to 可用于动词不定式和动名词结构中, can 不能.例如： I regret not being able to take his advice.4. can 表示有这种能力或机会,be able to 则表示经历一番艰难后能够做成某事.例如： The fire spread through the hotel very puickly but everyone was able to get out.三、may,mightmay 的用法：1. 表示许可.例如：May I come in ?2. 表示可能（可能性较 must 和 can 小）.例如：Peter may come with us tonight , but he isn't very sure yet.3. “may + have + 过去分词”表示对过去的推测.例如：You may have read some account of the matter. Otherwise how can you know about it ?might 的用法：1. may 的过去式.例如：He told me that he might go to Shanghai in a few days.2. 表示许可,比may 客气.例如：Might I use your pen for a short while ?3. 表示可能,比may 的可能性小.例如：Yessterday ,Jane walked away from the discussion. Otherwise ,might have said something she would regret later.四、shall, should shall的用法.1.用于第二、三人称,表示说话人的意愿,有“命令”、“警告”、“威胁”、‘“强制”意思.例如：You shall fail if you don't work hard.2.用于第一、三人称的疑问句,用来征询对方意见或请求指示.例如：Shall we begin our lesson?When Shall he be able to leave the hospital?should 的用法1.表义务或必然.例如： __ When can I come for the photos? I need them tomorrow afternoon.__ They should be ready by 12:00.2. 在名词性从句中表感情,即说话人认为应该如此.例如：It is natural that stuydents should study hard.3. “should + have +过去分词” 表示过去应该做而未做某事.含有惋惜、责备的意味.例如：We should have studied last night, but we went to the concert instesd.五、will ,wouldwill 的用法1. 表“意志”、“意愿”,用于各种人称.例如：I will do anything for you.2. 用于第二人称的疑问句中, 表示询问对方的意愿或向对方提出请求.例如：Will you do me a favour to carry the suitcase upstairs?3.表示习惯性的动作,有“总是”、“惯于”的意思.例如：Man will die without water or air.4. will do 表“够了”、“适合”、“行”等意思 .例如：__ Must I come here this Saturday?__ If you are busy that day, Sunday will do.would 的用法1. 表过去的意愿.例如：Though he would go to the south, his parents wouldn't let him.2. 表说话人的意愿或向对方提出请求,比 will 客气.例如：Would you please say that again?3. 表过去的习惯动作.例如： Whenever I passed his house I would see him standing under the big tree.4.“would like to +动词原形” 意为“愿意``````”.例如：Would you like to have a talk with me?六、must1. 表义务或强烈的劝告,意为“必须”、“应该”,否定式表示“禁止”、“不准”.在回答 must 的问句时, 否定回答用 needn't 或 don't have to .例如：You must finish your homework first.___ Must I do it now? ___ No, you needn't.2. 对现在情况的猜测用“must + 动词原形”.例如：You must be very tired now.3. 对过去情况的猜测用“must+have +过去分词”.例如：He must have been to Shanghai.七、ought to1. ought to =“should + 动词原形”,表“义务”、“劝告”.但语气比其强.例如：You ought to take care of him.2. “ought to + have + 过去分词” 表示过去应该做而未做的事情.例如：You ought to have helped him. (but you didn't)八、 dare ,need1. dare 和 need 都既有情态动词的功能,也有实义动词的功能. dare 用情态动词时常用于否定句、疑问句、和条件句中；need 作情态动词时用于否定句或疑问句中.例如： I wonder how he dared say that to the teacher. ___ Shall I tell John about it? ___ No, you needn't. I have told him already.2.need 构成一般疑问句时,其肯定回答用must ,否定回答用 needn't .例如：___ Need I do it now?___ Yes, you must. (NO, you needn't.)3.“need (not) +have +过去分词”表示“本有（无）必要做某事,然而做了（没有做）”.例如：You needn't have told him about the news. He had known it long before.