初中英语情态动词知识点及经典练习题情态动词知识点总结：（一）情态动词的定义情态动词表示说话人对动作的态度，比如：需要，可能，意愿，猜测或者怀疑等等。（二）情态动词的特点1）有一定词义；2）不受主语人称和数的变化影响；3）与主要动词的原形（或称不带to的不定式）一起构成谓语（除ought to作固定词组看待）。 4）否定句中，在情态动词后面加not。（三）情态动词有：must, shall, should, had better 词形无变化can(could), may(might), will(would) 词形有变化 need既可以是情态动词，也可以是实义动词，具有双重性。（四）情态动词的基本用法1. can (could)1）表示会做某事，有能力做某事。意思 = be able to其否定式cant表示“不能”。在过去时中用could和couldnt.（即有种能力，尤其是生来具备的能力，此时may和must均不可代替它）。He can speak English, but he cant speak Japanese.= He is able to speak English, but he isnt able to speak Japanese.I could smile but I couldnt speak when I was 2 months old. = I was able to smile but I wanst able to speak when I was 2 months old.区别：1、 can只用于现在时和过去时(could), be able to 可用于各种时态。They will be able to tell you the news soon. 2、be able to 不与can连用，但可以和其他情态动词或助动词连用。He may be able to speak English very well some day in the future. 3、用在过去时中，could经常表示能够做某事，事实上不一定去做，而waswere able to则表示“过去做成了某事”。在否定句中两者可通用。2）用于征求意见Can /Could /May /Might I(we) do sth?Yes, you can/may. / Of course you can.No(Sorry), you cant. /mustnt.注意：此处的could和might都不表示过去，只是语气上的委婉，不用作回答。否定回答中，表示对他人造成一定伤害或影响，或表示违反了某种规定或法律时，用mustnt较好。 e.g. Could I take the book out of the library? Sorry, you mustnt.May I smoke here? Im afraid you mustnt.表示过去能力时，could 提问，只能用could回答。 e.g. Could you ride a bike when you were 4 years old? No, I couldnt. 3）表提出意见或请求Can/Could you (please) do sth? = Would you (please) do sth? （此句型中some 不变any）e.g. Could you please give me a hand? Would you please pass me some salt?4）表示允许或承诺 =may e.g. OK. You can /may e and find me at any time tomorrow.5）表示有一定把握的推测，用于否定句和疑问句。此时cant译为“不可能” 肯定句用must。表示没有把握的推测，用may /might。e.g. The window is broken. Who did it? It may be Mary. It cant be Mary. The window is in the mens toilet. Can it be anyone else? Then, it must be Bob. I saw him go into the toilet just now.He cant (couldnt) have enough money for a new car. 他不可能有足够的钱买新车。【例题】I think Miss Gao must be in the library. She said she would go there.No. She _be there, I have just been there. A.cant B.mustnt C.neednt D.wouldnt【解析】根据下文“我刚去过那儿”可知，应为“不可能”，cant表示推测答案 A2. may (might)may 表示“可以，可能”，否定形式may not，表示“不可以”。1） 表示没有把握的推测，“可能，也许”。可以指过去时间，也可以指现在时间，但语气更加不肯定。e.g. He may have a lot of work to do. = Maybe he has a lot of work to do. You may be right. = Maybe you are right.2）表示请求 “我可以吗？”表示请求、许可，比can正式e.g. You may /can go now.May I use your pen? Yes, you may. / Yes, please. / Go ahead.No, you cant. / mustnt.在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly. / Please dont ./ Youd better not. / No, you mustnt.等，以免显得太严峻或不客气。3）、 表示希望、祈求、祝愿，常可译为“祝愿”。通常是用may +主+V例如：May you have a good time.祝你过得愉快。May you be happy!祝你幸福！May you succeed！祝你成功！3. mustmust 表示“必须，肯定，一定”， 否定形式mustnt = must not表示“禁止”。1）表示必须，意思同have to e.g. Must I do it now?Yes, you must.No, you dont have to. / No, you neednt. (注意：否定回答不用mustnt) Children mustnt play on the road because its too dangerous. (mustnt只表“禁止”) He doesnt have to go away from here. =He neednt leave here.区别：must表达主观意愿的“必须”，have to表达客观上或按道理说“不得不”。 e.g. I must study hard. Its too late. I have to go now.must 没有人称和时态的变化，而have to有。 e.g. He had to walk back home because he lost all his money. Mom will be away for a week, so we will have to do the cooking by ourselves.2）表示有把握的肯定句中的推测，“肯定，一定”，只用于肯定句。He must be ill. He looks so pale. 他准是病了。他的脸色苍白。注意其反意问句的构成形式：当must表示肯定的判断、推测时，其反意疑问句要用实际问句的助动词来构成。如：She must have seen the film before，hasntshe?(注意反意疑问句的后半部分)You must have met uncle Wang in the shop yesterday，didnt you? (注意反意疑问句的后半部分)4.needneed 表示“需要”，否定形式neednt = need not“不必、不需要”1)、作情态动词，仅用于否定句和疑问句。 e.g. He neednt go home early yesterday. = He didnt need/have to go home early yesterday. Need I call him right now? Yes, you must.(注意：肯定回答不用need)No, you neednt. /No, you dont have to.2）、作实义动词，此时有人称、数和时态的变化，如果是人作主语后边多接动词不定式：need sth./sb.need to do sth. 否定形式dont need to = dont have to 表示“不必” e.g. I need some help. He needed to go home early yesterday. Do I need to call him right now? Yes, you do. / No, you dont.如果是物作主语，一般用need doing与need to be done这种情况下应注意两点：.主动形式的动名词doing具有被动的含义；.该动名词可以改为其动词不定式的被动形式而句子的意义不变。例如：. The door needs painting. = The door needs to be painted.那扇门需要油漆一下。Your car needs mending. = Your car needs to be repaired.你的车需要维修了。3）、 need 作名词 be in (great) need of sth = need sth (badly) “非常需要某物”meet the need “满足需要（需求）” there is/was no need (for sb) to do sth “某人没必要做某事”5. dare的用法：dare意为“敢、敢于”,用法近似于need，有两种词性：（1）dare作为情态动词，多用于否定句、疑问句或条件句中，无第三人称单数形式，只有一般现在时和一般过去时。如：Dare he tell them what he knows?他敢告诉他们所知道的情况吗？I darent ask her will you do it for me?我可不敢问她，你能帮我问问吗？（2）dare作为实义动词，此时有人称、数及时态的变