情態(tài)動(dòng)詞:
　　may/might表示允許和可能:
　　允許: 詢問或說(shuō)明一件事可不可以做.
　　May I trouble you with a question?
　　You may take this seat if you like.
　　He asked if he might glance through my album.
　　You might as well speak your mind. (比may…顯得婉轉(zhuǎn)一些)
　　可能: 表示一件事或許發(fā)生(或是某種情況可能會(huì)存在).
　　You may walk ten miles without seeing a house.
　　She was afraid they might not like the idea.
　　A bad thing might be turned to good account.
　　might 表示請(qǐng)求:
　　Might I ask for a photograph of your baby? (比May I …更客氣一些)
　　can’t, couldn’t表示否定的推測(cè):
　　She can’t be serious.
　　A more suitable book can’t be found. (It is not possible to find a more suitable book.)
　　He couldn’t (can’t) be over fifty.
　　should, ought to: 表示應(yīng)該做的事, ought to比should口氣稍重一些.
　　You should (ought to) do as he says.
　　You shouldn’t (oughtn’t to) talk like that.
　　但這兩者間也有一些差別, 在表示責(zé)任, 義務(wù)等該做的事情時(shí), 常用ought to, 在表示某件事宜于做時(shí), 多用should, 在下面的句子中這兩個(gè)詞就不宜換用:
　　You are his father. You ought to take care of him.
　　We should not use too many big words in our everyday speech.
　　will, would
　　shall, should表示意愿
　　情態(tài)動(dòng)詞后接進(jìn)行式, 完成式和完成進(jìn)行式:
　　情態(tài)動(dòng)詞可以和動(dòng)詞的進(jìn)行式構(gòu)成謂語(yǔ), 表示”應(yīng)該正在…”, “想必正在…”這類意思:
　　Why should we be sitting here doing nothing?
　　This isn’t what I ought to be doing.
　　She might still be thinking about the question you raised.
　　They must (may) be waiting for us, let’s hurry up.
　　They can’t be using the room now.
　　情態(tài)動(dòng)詞有時(shí)和動(dòng)詞的完成形式構(gòu)成謂語(yǔ), 表示”應(yīng)當(dāng)已經(jīng)…”, “想必已經(jīng)…”這類意思:
　　I should have thought of that.
　　They shouldn’t have left so soon.
　　She must have arrived by now.
　　You needn’t have told them that.
　　Where can (could) he have gone?
　　He can’t have finished the work so soon.
　　He may not have achieved all his aims. But his effort is praise-worthy.
　　We ought to have give you more help.
　　情態(tài)動(dòng)詞間或也可以和一個(gè)動(dòng)詞的完成進(jìn)行式構(gòu)成謂語(yǔ),表示”應(yīng)當(dāng)一直在…”, “想必一直在…”這類意思:
　　They are sweating all over. They must have been working in the fields.
　　They may have been discussing the problem this morning.
　　You should have been waiting for us. Why haven’t you?
　　She couldn’t have been swimming all day.