1、情態動詞情態動詞表示說話人對某一動作或狀態的態度，認為“可能”“應該”“必要”等。情態動詞本身詞義不完全，不能單獨用作謂語，必須和不帶to的不定式（即動詞原形）連用。情態動詞沒有人稱和數的變化。情態動詞的否定式一般是在它們的后面加否定詞not構成。朗讀時，情態動詞的肯定式一般不重讀。一、 can和could的用法（一）can的用法1. 表“能力”。Eg. Our company can keep pace with changes in the market. Specially-trained dogs can smell out drugs.2. 表“許可”。Eg. - Can I use

2、 your mobile phone? - Im afraid not. I am expecting a call.3. 表“可能性”。多用于否定與疑問句中，但也可用于肯定句中表示理論上的可能性。Eg. Can there be life on Mars? You cant be tired -youve only been working for an hour. You cant have slept through that thrilling performance.4. 表其他。如“請求”“命令”“驚訝”“迷惑”“不相信”等態度。Eg. Can you help me to lif

3、t it, please? If you wont keep quiet, you can get out！ She has left her husband, but can you blame her after the way he treated her? You cant be serious!（二）could的用法：1. 表“過去能夠做某事”這樣一種事實，但不指具體的某次行為。Eg. I could read when I was three years old. He was so drunk that he couldnt find the front door.2. 表“過去

4、的可能與許可”。多用于間接引語中。Eg. Father said that I could go swimming in the river with my friends. Jack said he couldnt complete his collection in such a short time.3. 表“現在的可能與能力”。只是其可能性比must表示的可能性要小得多。Eg. My wife is in hospital. Our baby could arrive at any time.Whats for dinner? I could eat a horse.4. 表“現在的許

5、可”。主要用于疑問句（不可用于否定句），語氣比較委婉，其答語只能用can.Eg. -Could you baby-sit for us on Friday? -Of course, I can.5. 表“輕微的責備”。多用于第二人稱。Eg. You could be a bit more careful!6. 表“請求或命令”。多用于第二人稱。Eg. You could give me a band with the cooking.7. 表“建議”。Eg. If she is not at home, you could try phoning her at the office.二、 ma

6、y與might的用法1. 表“許可”。might可指現在的時間，也可指過去的時間，語氣更委婉。Eg. You may / might take whatever you like. He told me that I might borrow his dictionary. - May / Might I ask for a photo of your baby? - Certainly. 注意: 在回答may或might的問句時，應盡量避免使用may或might這個詞，而應用其他方式來回答。如：Yes, please. / Certainly. / Please dont. / Youd b

7、etter not. / No, you mustnt.等，以免顯得太嚴肅或太不客氣。2. 表“可能”。這時might和may可以互換，might可指現在的時間，也可指過去的時間，但語氣更加不肯定，即可能性更小。Eg. The road may / might be locked. She may /might be waiting for you in the entrance hall.3. might可用于虛擬語氣，may不能。Eg. If she were here, you might get some help from her. I might have told him the

8、 news if I had known it.4. may置于句首時表示愿望、祝愿，這也是虛擬語氣的一種特殊形式。Eg. May God bless you. May you succeed.5. 用于may/might as well結構中Eg. I might as well go. You may as well tell him what you think of him. His appearance had changed so much that you might as well not recognize him.三、 shall和should的用法(一) shall的用法

9、1. 多用于疑問句中以表示征求對方一件或指示，這時一般用于第一人稱和第二人稱。Eg. What shall we do this evening? Shall we go dancing? Shall he come to your office?2. 用于第二人稱和第三人稱，表“允諾”“警告”“命令”“決心”“必然”等。Eg. Dont worry. You shall get the book this afternoon. You are a naughty boy! You shall get what you deserve. He shall be punishes if he b

10、reaks the rule. Nothing shall stop us from carrying out the plan.(二) should的用法1. 表“義務，責任”。Eg. You should send her a note.2. 表“勸告或建議”。Eg. I often see lights in that empty house. Do you think I should report it to the police? Each of us should have a passionate pursuit in our life. We should learn abo

11、ut the computer and make full use of it.3. 表對現在貨將來比較有把握的“推測，推斷”。Eg. It is 8 oclock now. He should be here at any moment. I should have finished reading it by next Friday.4. Should與完成時連用，表示“過去應做而未做的事”。Eg. You should have told her about ir last week.5. 構成虛擬語氣。Eg. It is suggested that we should start o

12、ut early tomorrow morning. If it should rain, the crops would be saved. I am anxious that he should be well cared for.6. 與think，imagine，say等連用，表達不成熟的意見。Eg. I should say she is over forty.四、 will和would的用法1. 表“意愿”。will表示現在的意愿，would表示過去的意愿。Eg. KMT chairman Lien Chan has visited Nanjing and will continu

13、e his visit to Xian and Shanghai after Beijing. Present Bush yesterday announced that American forces would withdraw from Iraq.2. 表示征求意見或提出請求。Eg. Will you do me a favour? Would Sunday night suit you? Id like to see your new bike.3. 表示習慣和傾向性。Eg. June is known as Black June in China because high schoo

14、l graduates will take the most important exam in their life-the national college entrance exam. G id for gold, but gold will not buy everything.4. 表示“推測”。Will用于談論現在，would用于談論過去。Eg. They will climb the mountain and help collect rubbish to improve the environment. Every family would have some sort of

15、trouble.5. 表示“執意，決心”。Eg. The man who has made up his mind to win will never say “impossible”. He would do it, though I told him not to.五、 must和cant的用法（一） must的用法：1、 表示“必須”。mustnt譯為“一定不要，不準”。Eg. I must shut the door, or the dog will come in. Plants must have water in order to live. - Must I return yo

16、ur book this week? - Yes, you must. - No, you neednt.2、 表示“推測”。譯為“準是，一定是”。（1）“must+v.”表示對現在情況的推測。 Eg. He must be mad.（2） “must+have+過去分詞”表示對過去的推測。 Eg. She didnt come to school. She must have been ill.（3） “must+be+v.ing”表示對將來或現在進行時態動作的推測。Eg. According to the weather report, it must be raining tomorro

17、w. He must be watching TV. You must be joking.3、 表示“應當”。相當于should，ought to .Eg. You must say hello to her.4、 表示“偏偏”，表達對某事的不滿或責備等情緒。Eg. Why must it rain on Sunday？5、 表示抱怨或諷刺。“must+be+v.-ing”表示對將來或現在進行時態動作的推測。Eg. Why must you always be finding fault with me?（二） cant的用法：1. 表示“不能，不許”等。Eg. I cant swim in the lake. They cant wear jeans lake.2. 表示“推測”。（1） 表示對現在和將來的推測。Eg. Can he have said so? He cant have said so.（2） 表示對過去的推測。3. 用于某些固定結構，如：cant help doing sth表示“不禁，忍不住，不得不（做某事）”。Eg. Hearing the news, I cant help laughing.4. Cannottoo不論怎樣都不過分。