（一）情態動詞的定義
情態動詞表示說話人對某一動作或狀態的態度。
（二）情態動詞的特點
1）有一定詞義；
2）不受主語人稱和數的變化影響；
3）與主要動詞的原形（或稱不帶to的不定式）一起構成謂語（除ought to作固定詞組看待）。
（三）情態動詞的分類和意義意義情態動詞
（四）情態動詞的基本用法
1. can (could)1）表示能力，could主要指過去時間。Two eyes can see more than one. 兩隻眼比一隻眼看得清。Could the girl read she went to school? 這女孩上學前能識字嗎？
2）表示可能（理論上或是邏輯判斷上）。
The temperature can fall to -60℃, that is 60℃ below freezing. 氣溫可降至-60℃，也就是零下60℃。
He can't (couldn't) have enough money for a new car. 他不可能有足夠的錢買新車。
You mustn't smoke while you're walking around in the wood. You could start a fire. 在林子裏走時勿吸菸，那樣可能會引起火災。
3）表示允許。Can I have a look at your new pen? 我可以看一看你的新鋼筆嗎？He asked whether he could take the book out of the reading-room.他問他可不可以把書帶出閱覽室。
4）表驚異、懷疑、不相信等態度。主要用於否定句、疑問句或感嘆句中。
Where can (could) they have gone to? 他們會去哪兒了呢？
He can't (couldn't) be over sixty. 他不可能超過六十歲。
How can you be so careless? 你怎麼這麼粗心？
5）比較委婉客氣地提出問題或陳述看法。
Can (Could) you lend me a hand? 幫我一把好嗎？
I'm afraid we couldn't give you an answer today. 恐怕我們今天不能給你答覆。
2. may (might)
1）表允許，might可以指過去時間，也可指現在時間，語氣更委婉。
You may take whatever you like. 你喜歡什麼就拿什麼。
He told me that I might smoke in the room. 他告訴我可以在房間裏抽菸。
May (Might) I ask for photo your baby? 我可以要一張你寶寶的照片嗎？在回答以may引起的問句時，多避免用這個詞，而用其它方式，如Yes, please. / Certainly. / Please don't ./ You'd better not. / No, you mustn't.等，以免顯得太嚴峻或不客氣。
2）表可能（事實上）。可以指過去時間，也可以指現在時間，但語氣更加不肯定。
He may be at home. 他可能在家。
She may not know about it. 她可能不知道這件事。
He was afraid they might not agree with him. 他擔心他們可能不同意他的意見。
They might be having a meeting, but I'm not sure. 他們有可能在開會，不過我不肯定。
3. Must
1）表示義務。意爲"必須"（主觀意志）。
We must do everything step by step. 我們一切都必須循序漸進地做。
You mustn't talk to her like that. 你不可能那樣對她說話。
--Must we hand in our exercise-books now? 我們現在就要交練習本嗎？
--No, you needn't. / No, you don't have to. 不必。（這種情況下，一般不用mustn't）
2）表示揣測。意爲"想必、準是、一定"等，只用於肯定句。
He must be ill. He looks so pale. 他準是病了。他的臉色蒼白。
She's wearing a diamond necklace. She must have a lot of money. 她戴着鑽石項鍊，一定很有錢。
4. Shall
1）表徵詢意見，用於第一、第三人稱疑問句。Shall I get some tea? 我給你點茶好嗎？
Shall the boy wait outside? 讓那男孩在外面等嗎？What shall we do this evening? 我們今晚做什麼？
2）表說話人的意願，有"命令、允諾、警告、決心"等意思，用於第二、第三人稱陳述句。
You shall do as I say. 按我說的做。（命令）
You shall have my answer tomorrow. 你明天可以得到我的答覆。
（允諾）He shall be sorry for it one day, I tell you. 有一天他會後悔的，我告訴你。
（警告）Nothing shall stop us from carrying out the plan. 什麼也不能阻止我們執行這項計劃。（決心）
5. Will
1）表意願，用於各種人稱陳述句。I will do anything for you. 我願爲你做任何事。
None is so blind as those who won't see. 不願看的`人眼最瞎。
If you will read the這本書，我會把它借給你。
2）表請求，用於疑問句。
Will you close the window? It's a bit cold. 請你把窗戶關上好嗎？有點冷。
Won't you drink some more coffee? 再來一點咖啡好嗎？
3）表示某種傾向或習慣性動作。
Fish will die out of water. 魚離開水就不能活。 The door won't open. 這門打不開。
The boy will sit there hour after hour looking at the traffic go by. 那男孩常常坐在那裏好幾個鐘點，看着車輛行人通過。
6. Should
1）表義務。意爲"應該"（某件事宜於做），用於各種人稱。
You should be polite to your teachers. 你對老師應該有禮貌。You shouldn't waste any time. 你不應該浪費時間。
2）表推測，意爲"想必一定、照說應該、估計"等。
The film should be very good as it is starring first-class actors. 這部新電影是一流演員主演的，估計拍得很好。They should be home by now. 照說他們現在應當已經到家了。
d
1）表意I said I would do anything for you. 我說過我願意爲你做任何事。
2）表委婉地提出請求、建議或看法。Would you like another glass of beer? 再來杯啤酒好嗎？
Would you mind cleaning the window? 請把窗戶擦一下好嗎？
They wouldn't have anything against it. 他們不會有什麼反對意見。
3）表過去反覆發生的動作或過去的一種傾向。Every time she was in trouble, she would go to him for help. 她每遇到麻煩都會向她求助。他告訴我盒子打不開了。
8. ought to
1）表義務，意爲"應該"（因責任、義務等該做），口氣比should稍重。You are his father. You ought to take care of him. 你是他父親，應當管他。You oughtn't to smoke so much. 你不應該抽這麼多煙。
2）表推測，暗含很大的可能，語氣較弱。
Han Mei ought to know his telephone number. 韓梅該知道他的電話號碼。
There's a fine sunset; it ought to be a fine day tomorrow. 今天有晚霞，明天應該是個好天。
9. used to 表示過去的習慣動作或狀態，現在不復發生或存在。疑問式和否定式有兩種。
He used to live in the countryside, but now he lives in the city.他過去住在鄉下，現在住在城裏。
There used to be a building at the street corner, bn. 街道拐角處過去有座樓房，現在拆了。
I usedn't (didn't use) to smoke. 我過去不抽菸。
Used you (Did you use) to go to school on foot? 你過去常步行去學校嗎？
（一）need和dare的用法
need和dare既可用作情態動詞，也可用作實義動詞。用作情態動詞時，主要用於否定句和疑問句。用作實義動詞時，可用於各種句式。
1.用作情態動詞--Need I come? --Yes, you must. --我需要來嗎？ --需要。
You needn't telephone him now. 你現在不必打電話給他。
I don't think you need worry. 我想你不必發愁。
She dare not go out alone at night. 她晚上不敢一個人出去。
How dare you say I'm unfair? 你竟敢說我不公平？
Not one of them dared mention this. 他們誰也不敢提這件事。
2.用作實義動詞You don't need to do it yourself. 你不必親自做這件事。
We need to tell them the news. 我們需要把這消息告訴他們。
The table needs painting (to be painted.). 桌子需要油漆一下。
We should dare to give our own opinion. 我們要敢於提出自己的觀點。
He did not dare (to) look up. 他不敢擡頭看。
I dare day he'll come again. 我想他會再來的。（I dare say…爲固定習語）
（二）情態動詞後跟完完成這項工作的。
He isn't here. He must have missed the train. 他還未到，一定是沒趕上火車。
Where can (could) he gone? 他能到那裏去了呢？
You may (might) have read about it. 你可能在報上已經讀到這件事了。
You could (might) have been more careful. 你本來可以更細心的。
He needn't have worried it. 他本不必爲此事擔心。
There was a lot of fun at yesterday's party. You ought to have come, but why didn't you? 昨天的聚會非常有意思。你本應該來，爲何不來呢？
2. 情態動詞後跟進行式，表示"想必正在……"，"可能正在……"，"應當正在"等意。It's twelve o'clock. They must having lunch. 現在是十二點。他們一定正在吃飯。
