①此时可用be able to代替。 ②Can只有一般现在时和一般 I’ll not be able to come this 过去式；而be able to则有更 afternoon。（更多的时态） 多的时态。 He was able to go to the party ③当表示“经过努力才得以做 yesterday evening in spite of the heavy rain. （经过努力才得以做成功某） 成功某事”时应用be able to，不能用Can。was/were able to to表示成功做了某事 Yes, you can. 在请求允许的用法中，could No, you can’t. 并不是过去 时，它指的都是 Yes, you can. ( No, I’m afraid not. ) 将来时，虽然请求用could 语 Yes, of course you can.（肯定回答句 气委婉，也允许不用 could. 中，不能用 could ）
may
might ②表示推测、可能性（不用于 He may /might be very busy now.
疑问句）。 ③用于祈使句，表示祝愿。 ① 表示必须、必要；说话人 “不许”和“禁止”某人做某 事，有很强的劝告语气。 ② must是说话人的主观看 法， 而have to则强调客观需 Your mother may /might not know the truth. May you succeed! You must come in time. Must we hand in our exercise books today?
can
②表示请求和允许，用could Can I go now? could 要比用can更加迟疑不决，当 Could I come to see you tomorrow? 你没有把握 得到允许时，这 Could I give you dinner one of these days? 样更婉转。 ③表示客观可能性 They’ve changed the timetable, so we can go by bus instead. This hall can hold 500 people at least.
need
dare
③ dare和 need作实义动词用 时，有人称、时态和数的变化 I dare to swim across this river. 。在肯定句中，dare后面常接 He doesn’t dare (to) answer. 带to的不定式。在疑问句和否 He needs to finish his homework today. 定句中，dare后面可接带to或 不带to的不定式,而need后面 只能接带to的不定式。 Did you use to go swimming in the river when you were young?（你小时候经常在河里游泳吗?） ①表示过去常常做某事,强调 Used he go to school by bike?（他过去骑车上学 现在已经不存在的习惯,它只 吗?） I used to go to the 用于过去时态。 cinema,but I never have time now. He used to listen to pop music but now he likes rock music. Used you play basketball?（你过去常打篮球吗?） Yes, I used to.(No,I usedn't.)（是的，经常打 / 不，不常打。) I don't write to him now, but I used to. (我现在不给他写信了，但过去经常写) He is used to hard work．（他习惯于艰苦工作） He was used to the cold weather after he lived there for two years．（ 在那里住两年后，他已习 惯了寒冷的天气） They got used to living in the countryside． （他们已习惯于住在农村） I've got used to being a vegetarian．（我已经习 惯吃素食） I think it is a bit difficult for you to get used to the humid weather here．（ 我想，让你习惯于这里潮湿而炎热的天气有点困难） You'll soon get used to living in the country． （很快你就会习惯于住在乡下了 ） A metal bar was used to force the door open． （用金属棒把门撬开） The threshing ground was used to hold a mass meeting． （打谷场曾用于举行群众大会） You had better not miss the last bus. You'd better get some sleep．（你最好去睡一会 （你最好不要错过末班公共汽车） 儿） We had better go before it rains.（我 You had better not leave for Nanjing 们最好在下雨前就去）(这里的had不能用have来替换) the day after tomorrow.（你最好后天不 要动身去南京） Now you(he，we) had better listen to the teacher.（你/他/我们现在最好听老师讲) Hadn't you better take an umbrella?(你 不认为该带一把伞吗? ) Hadn't you better ask him first?(你不 认为该先问问他吗?) 常用的否定形式，将否定副词 not直接放在had better的后 面。 had better的疑问式，常用： Hadn't+主语+better...?的结 构,作为一种劝告形式，比肯 定形式的语气更婉转一些。
What are modal verbs?（ 什么是情态动词）
情态动词 词义 例句 更多表达形式 注意事项
Can you lift this heavy box?（体力） ①表示能力（体力、知识、技 Mary can speak three languages.（知识） 能） Can you skate?（技能）
①can用于否定和疑问句 (could不限) ② can (be)表示有时候会（常与 sometimes, at times 连用） Yes, you can. / sure / certainly / of ①用May I...？征徇对方许可 course /You may indeed（不能用 might） 时比较正式和客气，而用Can 。 I...？在口语中更常见。 No, you can’t / mustn’t/ may not. 此意常用于肯定句。（might 可能最小） 固定句型为“May+主语+V原型 ”： Yes, you must. No, you don’t have to / you needn’t. (否定句不能用mustn’t禁止，不准） Must只有一般现在时， have to 有更多的时态形式。 只用于肯定句。在否定句/疑 问句中用can/could 此意用于疑问句，常与you连 用 Would此时为will过去式，无 意义差别
always, never, really 可以 放在ought 前面和后面。前面 比较常见。
肯定的语气没有must用于推测 时强
I wonder whether he dare stand up in public. I don’t know how she dares to wear that dress. 多用于肯定句: Yes, you must. No, you needn’t. You needn’t come so (sb.) need to do/ dare to do early. (sth.) need to be/ done
叙述真理：The tree will leave without water for 3 months.
Passengers shall not talk with the driver while the bus is moving
shan't=shall not（不应该 （*只适用于英国英语） 用于所有人称

③would表示过去反复发生的 During the vacation, he would visit me every will would 动作或某种倾向; would表示 other day. 过去习惯时比used to正式， The wound would not heal. 且没有“现已无此习惯”的含 It would be about ten o’clock when she left ④ 表示估计和猜想，对目前 home. That 事物的预料。 will be the postman ringing.(would表示过去/现 在；will表示现在/将来) ① shall 用于第一人称，征 What shall we do this evening? 求对方的意见，意思是好不好 Shall the reporters wait outside or what? 。 Shall you do some shopping with me? ② shall 用于第二、三人 You shall fail if you don’t work hard.(警告) shall 称，表示说话人给对方的命令 He shall have the book when I finish it.(允诺) 、警告、允诺或威胁。 He shall be punished.(威胁) ③表规章、法令、预言：“必 Every competitor shall wear a number 须” You ought to /should pay more attention to what should ① should, ought to表示“ your lawyer says. (与shall 应该”，ought to表示义务或 You should stay here as long as you like. ought to词义 责任，比should语气重。 I should help her because she is in trouble. 互通） You ought to take care of the baby. ② 表示劝告、建议和命令; You should / ought to go to class right away. should, ought to可通用，但 You always ought to carry some spare money. 在疑问句中常用should。 Should I open the window? He must be home by now. (断定他已到家) He ought to/should be home by now.(不太肯定) ought to ③ 表示推测时，should , This is where the oil must be.(直爽) ought to (客观推测), This is where the oil ought to/should be.(含蓄) must(主观推测)。 You are mistaken , I should say . (依我看你是 搞错了) This pen ought to /should be yours.(不太肯定) How dare you say I’m unfair? ① dare表示敢于，主要用于 He daren’t speak English before such a crowd, If we dared not go there that 否定句和疑问句中和条件从句 dare he? day， we couldn’t get the beautiful flowers. I 中, 过去式形式为dared。 daren’t ask her for a rise. How did you dare to tell her that? ② need 表示需要、必须，主 要用于否定句和疑问句中；在 Need I finish the work today? need dare 肯定句中一般用must, have Do you need any help? to, ought to, should代替。