2016年職稱英語衛(wèi)生類備考語法：情態(tài)動詞

關于情態(tài)動詞：

①常見的情態(tài)動詞有：can (could) ,may (might), must ,shall (should), will (would), dare (dared) , need等,另外,have to、had better也當作情態(tài)動詞使用。情態(tài)動詞后面必須加動詞的原形。

②can表示體力、腦力方面的能力或客觀的可能性�？谡Z中, 在詢問或說明一件事可不可以做時,常用“can”代替“may”。情態(tài)動詞“can”的過去式是“could”,否定式是“cannot”通常縮寫成“can't”,“could”的否定式是“could not”,通�？s寫成“couldn't”。如：Can I help you?(要幫忙嗎?)/ He can swim.(他會游泳)/ That can't be Mr Li.(那不可能是李先生)

③ may表示允許、請求或可能性,用may提問時,肯定回答一般用Certainly或Yes,you may.;否定回答一般用can't或mustn't. 如：May I ask you a question?—Certainly.(可以問你一個問題嗎?當然可以)/ You may go now.(現在你可以走了)/ It may be in your pocket.(它可能在你的衣袋里)

④ must表示“必須”、“一定”的意思。表示“必須”時否定形式是mustn't;表示“一定”時,否定形式是“can't” 如：We must be very careful when we cross the road.(我們過馬路時一定要非常小心)/ It must be Jack.(那準是杰克)/ I haven't seen Kate today. She can't be here.(我今天沒有看到過凱特,她不可能在這里)

[注意]用must(必須)進行提問時,肯定回答用must,否定回答用needn't;用must(一定)進行提問時,肯定回答仍用must,但是否定回答用can't.如：Must we clean the room before we leave? –Yes, you must.或No, you needn't.(我們走之前必須要打掃房間嗎?是的,必須打掃。/ 不,不需要。) / Must she be in the room? –Yes, she must.或No, she can't.(她一定在房間里嗎?是的,一定。/ 不,不可能在。)

⑤ “have to”表示“不得不”、“必須”。We'll have to leave now for it is very late at night.

have to的疑問形式是：助動詞+…+have to,否定形式是：助動詞+not+have to或者用needn't.如：Do you have to stay until 8 o'clock?(你得呆到8點鐘嗎?)/ You don't have to do so.(=You needn't do so.)(你不用這么做)

⑥ shall在問句中,可表示征求對方意見,與第一人稱連用;在陳述句的第二、三人稱的主語后或表示“命令”、“警告”、“允許”等。如：Shall we go to the zoo this weekend?(我們這個周末去動物園好嗎?)/ He shall bring his own book next time.(他下次必須帶自己的書來)

⑦ should可表示“勸告”、“建議”、“驚奇”等意思。We should speak to old people politely.(我們應該禮貌地對老人講話)

⑧ will表示“意愿”、“決心”等意思,一般與第二人稱連用。如：Will you please close the door for me?(請你替我把門關上好嗎?)/ I will teach you a lesson.(我要教訓你一頓)

⑨would表示過去的“意愿”、“決心”等。He would sit near the fire every time he returned home.(每次他回到家中總要坐在火爐邊)

would也可以表示現在的情況,表達說話人向對方提出的要求,語氣比“will”婉轉、客氣。在日常會話中,“我想要…”通常用“I would like to”或“I should(I'd) like to”來表示。如：Would you like to have a rest at the moment?(你現在想要休息一下嗎?)

would還可以表示過去經常發(fā)生的事情。如：Every year parents would tell their children about the boy who would save his people.(每一年父母們總是向孩子們講述這個將會拯救他的人民的男孩的事)

⑩ need表示“需要”,用于疑問句或否定句。“need”作實義動詞時,在肯定、否定、疑問句中都可以用。如：He needn't do it in such a hurry.(他不需要如此匆忙地做這件事)/ He needs some help.(他需要一些幫助)/ He doesn't need to bring his football socks then.(那么他就無須帶上足球襪了)

⑾ dare是“敢”的意思,用法幾乎與“need”完全相同,即在疑問句和否定句中,可以作情態(tài)動詞,后面用不帶“to”的動詞不定式。在肯定句中和實義動詞一樣,后面的動詞不定式要帶“to”。How dare you say I am a fool?(你竟敢說我是個傻瓜?)/ He didn't dare to touch the red button.(他不敢觸碰那個紅色的按鈕)

⑿ ‘d better (do)(“最好是”)一般也當作情態(tài)動詞使用,否定式是：'d better not (do). 如：You'd better sit here and say nothing.(你最好坐在這兒不講話)/ You'd better not speak because he is sleeping.(你最好不要講話因為他正在睡覺)