情态动词虽然算是初中英语词汇，是从刚开始学英语就接触到的基本词汇。但要用得和Native Speaker 一样准确，要用的准确表达出自己的强弱心态，却是我们需要额外下功夫的。今天给大家详细解析一下四组易搞混的情态动词must vs have to; should vs ought to; can vs could; may vs might,同学们可不要再用错啦~ Must用法：1) Obligation 义务E.g.: You must wear a seatbelt when you drive.你开车的时候必须系安全带。2) Deduction猜测这里要注意的是，如果用must，那么代表你很肯定你的猜测是正确的。E.g.: Look at all that snow. It must be cold outside.看看那些雪，外面肯定很冷。3) Emphasize necessity 强调必要性E.g.: Plants must have light and water to grow.植物需要光和水才能生长。4) Strong recommendation 强烈建议E.g.: We must get together for dinner soon.我们一定要尽快一起吃饭。5) Mustn’t = prohibition 禁止E.g.: You mustn’t use your phone while driving开车时禁止使用电话。 MUST vs HAVE TOMustMust express obligation imposed by the speaker while HAVE TO expresses external obligations.Must表达了说话者所施加的压力。Have to表达了外部的压力Have toWe use had to instead of must in the past tense. 在过去时态中，我们用had to代替must。
E.g.: Your teacher may say ‘you must complete this essay by Friday.’, while you say ‘we have to complete the essay by Friday.’老师说的“必须要在周五前完成论文”和学生自己说的“必须要在周五前完成论文”，大家自行感受下…E.g.: I had to pay my speeding ticket yesterday.我昨天不得不交了超速的罚款。It is more common to use have to instead of must in questions. 在问句中，have to 常被用来代替must.E.g.: Does he have to do the test?他一定要参加那个测试吗？ Mustn’t vs don’t have toBe careful: there is a difference in meaning between mustn’t and don’t have to. Mustn’t 和 don’t have to意思不同哦~Mustn’tMeaning：It is prohibited; it is not allowed. It is important that you do not do something.. Don’t have toMeaning：There is no obligation; you are not required to do something, especially if you don’t want to.了解了mustn’t和Don’t have to的意思之后，我们来具体看一下这两个词的用法吧！有实例才能更好的了解词语间的不同哦~You must not drink that.= Don’t drink that, it is not allowed.VSYou don’t have to drink that.= You don’t need to drink that but you can if you want to. You mustn’t tell john. = do not tell john VSYou don’t have to tell john.= you can tell john if you want to but it is not necessary Should用法：1) Advice or suggestion 意见或建议E.g.: Your hair is too long. Yu should get a haircut.你头发太长了，你用过剪个头发。2) Situation likely in the present 现在发生的情况E.g.: Mary should be at home now. Give her a call.Mary现在应该在家，打个电话给她。3) Likely in the future（预测）可能发生在将来E.g.: They should win tonight, they are the better team.他们应该能赢，他们是强队。4) Should + have + past participleMeaning: the subject did not fulfil their obligation in the past or did not act responsibly. 在过去就应该做的，但没有尽职。E.g.: You should have given your boss the report yesterday when he asked for it.你应该在你老板昨天要的时候就把报告给他。5) Should + be + verb-ingMeaning: the subject is not fulfilling their obligation now or is not acting sensibly. 并没有尽义务，行为并不明智。E.g.: You should be wearing your seatbelt.你应该系安全带的。E.g.: We should be studying for the test right now.我们马上应该复习考试。 Should vs ought toShouldShould can be replaced by ought to without a change in meaning。Ought to能够替代should，而句子意思不改变。E.g. You ought to study more = you should study moreOught toNote: ought to sounds more formal than should and is used less frequently. Ought to 相较于should听起来更正式。
We use shouldn’t to advise not to do something, usually because it is bad or wrong我们用shouldn’t表示不建议做某事，因为事情本身不好，或者是错的。E.g.: You shouldn’t throw your litter onto the street.你不应该把垃圾扔在马路上。E.g.: You shouldn’t work so much.你不应该工作那么多。 Can用法：1) General ability (present) 能够（现在）E.g.: I can speak English.我能讲英语。2) Ask for permission (informal) 征求允许 （非正式）E.g.: Can I borrow your pen please?我能借你的笔吗？3) To request something 请求做某事E.g.: Can you help me please?你能帮我忙吗？4) Possibility 可能性E.g.: It can get very cold there at night.晚上可能非常冷。6) Offer to help someone 为某人提供帮助E.g.: Can I carry your bags for you?我能帮你背包吗》7) Cannot (can’t) = not allowedE.g.: You cannot smoke in this room.这个房间里不能吸烟。E.g.: You can’t go to the party.你不能去party Could1) General ability in the past 能力（发生在过去）E.g.: I could play the piano when I was younger.我小时候能够弹钢琴。2) Ask for permission (more polite) 征求允许（更礼貌）E.g.: Could I use your bathroom please?我能用你的洗手间吗？3) To request something (more polite) 请求别人做某事（更礼貌）E.g.: Could you pass me the salt please？麻烦你把盐递给我吧。4) Possibility in the past (could + have + past participle) 过去发生某事的可能性E.g.: You could have broken your leg.你可能腿断了。5) Suggestion (when asked what to do) 建议（当被问及做什么时）E.g.: We could go to the movies if you like.我们能去看电影如果你愿意的话。6）Condition of can (would be able to) 虚拟语气E.g.: If we had some oranges I could make you some fresh juice (= would be able to) 如果我们有橙子的话，我能给你做一些鲜橙汁。 May vs might共同用法：1) Possibility 可能性E.g.: It might rain later so take an umbrella.等一下可能会下雨，带把伞。2) Give permission 给予允许E.g.: You may have another cookie if you like.你喜欢的话可以再吃一片曲奇。3) Ask for permission 征求允许E.g.: May I borrow your pen please?我能借用你的笔吗？4) Express wished 表达祝福E.g.: May the New Year bring you happiness.祝你新年快乐。5) Speculate about past actions 对过去行为的猜测E.g.: She is late. She may have missed her plane.她迟到了。她可能误机了。 May or mightMay and might can normally be interchanged without a significant difference in meaning. However, might often implies a smaller chance of something happening (when expressing possibility).May和might意思并没有特别大的差别，一般情况下能够互相替换。但当表示可能性的时候，might发生的几率更低。E.g.: It may rain. (60%) It might rain. (30%)When expressing wished or giving permission, only may is used.当表达祝愿或是给予允许时，只能用may。
