情态动 情态动词( model verb)用来表示能力 允许、可能、必须、劝告、意愿等概念或态 度。主要的情态动词有can( could),may (might), shall (should), will (would) must, ought to,need,dare等。情态动词没有 人称和数的变化,其后常跟不带to的不定式
情态动词 情态动词（model verb）用来表示能力、 允许、可能、必须、劝告、意愿等概念或态 度。主要的情态动词有can （could），may （might），shall （should），will （would）， must，ought to，need，dare等。情态动词没有 人称和数的变化，其后常跟不带to的不定式
1.情态动词的一般用法: ●(1)表示能力:can, could, be able to o he is over 80 but still can read without glasses She couldn't come yesterday ● He can' t come tomorrow
1. 情态动词的一般用法： ⚫ (1) 表示能力: can, could, be able to ⚫ He is over 80 but still can read without glasses. ⚫ She couldn't come yesterday. ⚫ He can’t come tomorrow
●can/ could与 be able to用法比较 ) be able to除有一般现在时、一般过去时、一般将来 时外,还可有现在完成时、不定式、动词-ng形式等。 o This is the information Ive been able to get so far To be able to ride a bike, she practiced a lot Just being able to drive a horse, a cart isnt much help to 2) could表示过去总的、经常性的能力 was/were able to表示过去具体情况下具有的能力,并且做了某动作。 He could speak French. so he was able to show the French lady the way ●3)表示将来的能力常用 will be able to When will you be able to take us to town?
⚫ ⚫ can/could 与be able to 用法比较 ⚫ 1）be able to 除有一般现在时、一般过去时、一般将来 时外，还可有现在完成时、不定式、动词-ing 形式等。 ⚫ This is the information I’ve been able to get so far. ⚫ To be able to ride a bike, she practiced a lot. ⚫ Just being able to drive a horse, a cart isn’t much help to us. ⚫ 2) could表示过去总的、经常性的能力；was/were able to 表示过去具体情况下具有的能力，并且做了某动作。 ⚫ He could speak French, so he was able to show the French lady the way. ⚫ 3) 表示将来的能力常用will be able to. ⚫ When will you be able to take us to town?
(2)表示许可: can/could, may/might;cant,may not. mustnt. must not ●1)征询“许可”或给予“许可”可用 can/could或 may/might表示 May用于正式场合,can用于非正式场合, could用于客气的询问 might极少用。 You can go at four o'clock Could i borrow your pen? Students may take 3 books each o Might I ask whether you are using the typewriter? ●2)表示“不允许”用cant, may not, mustn t; must not语气重。 You cant leave the table unless you finish your meal Put that cigarette out. You must not smoke near a petrol pump 3)表示过去“许可”不用 could, might,要用其他表达方式 We had been/were given permission to speak to the patient 但在间接引语中表达过去“许可”,可用 could, might The nurse said that we could/might speak to the patient for just a few minutes
(2) 表示许可：can/could, may/might; can’t, may not, mustn’t, must not ⚫ 1) 征询“许可”或给予“许可”可用can/could 或may/might 表示。 May 用于正式场合，can 用于非正式场合，could 用于客气的询问， might 极少用。 ⚫ You can go at four o’clock. ⚫ Could I borrow your pen? ⚫ Students may take 3 books each. ⚫ Might I ask whether you are using the typewriter? ⚫ 2) 表示“不允许”用 can’t, may not, mustn’t； must not 语气重。 ⚫ You can’t leave the table unless you finish your meal. ⚫ Put that cigarette out. You must not smoke near a petrol pump! ⚫ 3) 表示过去“许可”不用could，might，要用其他表达方式。 ⚫ We had been/were given permission to speak to the patient. ⚫ 但在间接引语中表达过去“许可” ，可用could，might。 ⚫ The nurse said that we could/might speak to the patient for just a few minutes
3)表示可能性:may/ might,can/ could,must can t 1)may,migt用来推测现在“可能”;may比 might表示的可 能性大些。 o Why isnt John in class? He may/might be sick ● maybe是副词,不是情态动词。 Maybe he ●2)在日常口语中常用 can/could表示“可能” o You can/could walk for miles in the country without meeting anyone e Can the news be true? No it cant be true ●3)mus表示可能性最大,“必定”;否定形式用can?t表示 肯定不”、“必定不会” o You must be hungry after a long walk o The phone is ringing, but there is no answer. She cant be at home
(3) 表示可能性：may/might, can/could, must; can’t ⚫ 1）may, might 用来推测现在“可能” ；may比might表示的可 能性大些。 ⚫ Why isn’t John in class? He may/might be sick. ⚫ maybe是副词，不是情态动词。Maybe he is sick. ⚫ 2) 在日常口语中常用can/could 表示“可能” 。 ⚫ You can/could walk for miles in the country without meeting anyone. ⚫ Can the news be true? No, it can’t be true. ⚫ 3) must表示可能性最大， “必定”；否定形式用can’t表示 “肯定不” 、 “必定不会” 。 ⚫ You must be hungry after a long walk. ⚫ The phone is ringing, but there is no answer. She can’t be at home