will和would表示決心、意志、意愿等,用于各種人稱:

　　I will make the computer work even if I have to stay up all night. 哪怕我熬夜也要修好電腦。

　　She will help you if you can’t finish cleaning the classroom before 5:00. 如果你在5:00前不能完成打掃教室的任務(wù),她會(huì)幫助你的。

　　表示推測(cè)的情態(tài)動(dòng)詞有must, can, could, may, might, should等。must表示推測(cè)時(shí),意思是“一定、準(zhǔn)會(huì)”,語氣肯定,有把握,只能用于肯定的猜測(cè),可以推測(cè)現(xiàn)在正在發(fā)生的動(dòng)作和過去發(fā)生的動(dòng)作。can和could表示推測(cè)時(shí),往往用于否定句或疑問句,can’t表示“一定不”。

　　may, might表示推測(cè)時(shí),意思是“可能、也許”,語氣沒有must肯定。may, might表推測(cè)時(shí),還可以用于否定句,意思是“可能不、也許不”,但不用于疑問句。might不表示過去時(shí)態(tài),只是語氣上比may更委婉,表示可能性更小。should表示推測(cè)時(shí),其語氣比較肯定,并暗示其推測(cè)有一定的事實(shí)依據(jù)或者合乎客觀常理。例如:

　　This book should be found easily in the library. 在圖書館應(yīng)該很容易找到這本書的。(說話人認(rèn)為,圖書館應(yīng)該有很多這類書籍,所以應(yīng)該很容易找到。)

　　He must have enjoyed the film Avatar, otherwise, he wouldn’t want to see it a second time. 他一定很喜歡電影《阿凡達(dá)》,否則他就不會(huì)再想看第二遍了。

　　—Someone called you while you were away, but he didn’t say who he was. 你不在時(shí)有人打你電話了,但他沒說他是誰。

　　—Thanks. Who can it be?謝謝!他會(huì)是誰呢?

　　Look at that car! It must be driving at least 150 kilometers an hour. 看那車開得多快!起碼每小時(shí)150公里。(must be driving表示對(duì)現(xiàn)在正在發(fā)生的事情的肯定猜測(cè))

　　There is no one in the classroom. All the students must have gone to the Charity Bazaar. 教室里沒有一個(gè)人,學(xué)生一定都去Charity Bazaar了。(must have gone表示對(duì)過去事情的肯定猜測(cè)) could have done / might have done“本來能夠做而實(shí)際上沒有做”,用來表示對(duì)過去沒有做成某事的遺憾或責(zé)備;should have done / ought to have done“本應(yīng)該做某事而實(shí)際上沒有做”,用來表示責(zé)備或后悔;shouldn’t have done / ought not to have done“本不應(yīng)該做某事但卻做了”,用來表示責(zé)備或后悔;needn’t have done“本來不必做卻做了某事”。例如:

　　You should / ought to have come to the meeting earlier. 你應(yīng)該早點(diǎn)來開會(huì)。

　　He shouldn’t / ought not to have treated his parents like that. 他不應(yīng)該那樣對(duì)待自己的父母。

　　As you worked late yesterday, you needn’t have come this morning. 因?yàn)槟阕蛲戆疽构ぷ?沒有必要今天上午來的。

　　—I stayed at a hotel while in London. 在倫敦期間我住在旅館。

　　—Oh, why not contact Grace? You could have stayed at her home. 哦,你為何不聯(lián)系格雷西?你本來能住她家的呀!

　　should意為“竟然”,表示驚奇、遺憾:

　　I’m surprised that you should be late today. 我很驚訝你今天竟然會(huì)遲到。

　　need表示“需要,必須”,多用于疑問句和否定句中:

　　—Need we buy a laptop?我們有必要買筆記本電腦嗎?

　　—No, we needn’t. / Yes, we must. 沒有必要。/ 有必要。

　　dare表示“敢”,多用在疑問句和否定句中:

　　Dare you swim across the river?你敢游到河對(duì)面去嗎?

　　She dare not speak in public. 她不敢在公共場(chǎng)所說話。

　　need和dare作為行為動(dòng)詞時(shí),其變化與一般動(dòng)詞相同。作實(shí)義動(dòng)詞的dare在否定句中其后的to可以省略:

　　We need to think it over. 我們需要仔細(xì)思考。

　　She didn’t need to do such a part-time job to cover her tuition expense. 她沒必要打工去掙學(xué)費(fèi)。

　　—Who dares to go? 誰敢去?

　　—I don’t dare (to) ask her. 我不敢去問她。