1、1助动词和情态动词助动词包括：be (is, am, are, was, were, been, being)；have (has, had, having)；do (does, did)；shall (should), will (would)情态动词包括： can, could, (be able to)；may, might； will ,would； dare, need, must (have to)， ought to, shall, should“ be + 动词不定式 “可以表示下面几种意思 :1.命令或指示。例如：No one is to enter the room wit
2、hout permission.The books are not to be taken out of the reading-room.2.计划或安排。例如：A new bridge is to be built over the river soon.The expedition is to start in a weeks time.3.可能。例如：This kind of tree is to be found in that forest.4.应该。例如：Such people are to be criticized.5.表示后来发生的事，可以用来表示一种命运。例如：They s
3、aid good-bye, little knowing that they were never to meet again.He was to regret the decision.Note:was (were) + 不定式完成式2这种结构表示“本来打算，本来要（而结果则没做） ”。例如：He was to have attended the meeting, but he fell ill.他本来要参加会议的，但是生病了。 （因此没参加）have to 和 must 在表示“必须”这个意思时是很接近的，但也有一定的区别。1. have to 比较强调客观需要，表示因客观环境或事态促使而
4、不得不做某事；must 强调主观看法，表示主观上认为有必要做某事。例如：I must learn another language.（主观想法: I want to）I have to learn another language.（客观需要：身为一个外交官）You must be back before 10 oclock. （叮嘱或命令）You have to be back before 10 oclock because the train is to leave at 10:05.（客观需要）注意下面两句的含义：Though she didnt need to, she must g
5、o.虽然她不用去，她却偏要去。You dont have to come again, but you must.你不必再来，可是你执意要来。2. have to 多表示义务或习惯动作；must 则用于表示一种重要或急迫的事情。例如：3We have to care for the young.（义务）She has to be at the office before eight every day. （习惯）You must go to the manager at once, or youll be dismissed.务必马上去见经理，不然你会被开除的。 （急迫的事情）3. have
6、to 可用于不同的时态；而 must 一般只用于现在时（但也可以表示将来的情况，在间接引语中也可以表示过去时） 。例如：I have to (must) leave now.Well have to buy another TV set.They had to put off the sports meet because of the bad weather.He said that the work must be finished within two weeks.4. must 还可以表示一种推断和揣测，而 have to 则不能。例如：This must be Jins pen.Th
7、ere must be something wrong with the machine.5. “must动词完成式“可以用来表示对过去情况的 揣测，而 have to 则不能。例如：She must have read the book sometime in the past, or she couldnt have answered the question so well.她一定在过去某个时候读过这本书，不然，这个问题她不会回答得这么好的。Note:在现代英语中，have to 中不定式和疑问句式既可以按照助动词的变化规则构成，也可以按照行为动词的变化规则构成。例如：Have you
8、to finish the work before supper?Do you have to finish the work before supper?have got to 常可同 have to 换用，但有时表示不同的含义。比较：4He has to report to the headquarters every two days.（例行公事，习惯动作）He has got to report to the headquarters every two days.（一道指示或命令，必得每天报告一次）另外，作“有”解时，have got 和 have 通常是可以换用的，have got
9、 更口语化，但有时表示不同的含义。比较：The man has a blind eye.那人有一只眼瞎了。The man has got a blue eye.那人有一只眼被打青了。must not 表示禁止，是说话人强有力的劝告或命令，意为“一定要，不准” 。因此，在回答由 must 引导的问题时，如果是否定的回答，表示“不必，没有必要” ，不能用 mustnt，而要用 neednt 或 dont have to.试比较：You must not drive fast.你不能开快车。 （路险或有速度限制）You neednt drive fast.（时间充裕）You must not tel
10、l others.（警告）You neednt tell others.（没有必要）needs 为副词，相当于 necessarily, of necessity. must needs 和 needs must 均可表示 “必须，必定，不得不” ，这层意义上可以通用；但must needs 还可表示“偏偏，偏要” ，含有讥讽、不满的意思，而needs must 则一般无这层意思。例如：I must needs go there now.我现在非到那里去不可。 （可用 needs must）Needs must when the devil drives.情势所迫不得不那样。5She must
11、 needs go away when I want her.我正需要她时，她偏偏离开了。 （不可用 needs must）The telephone must needs ring when I went to bed.我上床睡觉时偏偏有人来电话。 （不可用 needs must）need 指主语的主观特需情况而使之必要。need 既可以作助动词，又可以作行为动词。作助动词时，need 没有人称和数的变化，后接不带 to 的不定式（动词原形） ，否定式为 neednt.作行动动词时，need同别的行为动词一样，有人称和数的变化，后接带 to 的不定式，否定式要在前面加 dont（doesnt
12、, didnt） ，疑问句用 do (does, did) 提问。例如：There need be no hurry, need there?He need never know. (=He never needs to know.)I need only add a few words. (= I only need to add a few words.)比较：Father sent me the book, so I didnt need to write to him for it.父亲把那本书寄来了，所以我不必为此给他写信了。 （信没写）Father sent me the book
13、, so I neednt have written to him for it.父亲把那本书寄来了，所以我本不该为此再写信给他的。 （信已写）She didnt need to come.她不必来的。 （实际也没来）She neednt have come.她本来不必来的。 （但却来了）Note:作助动词用时，need 只用于疑问句中和否定句中，在肯定句中常用 must, have to, should, ought to 等。例如：Need you do it right now? I neednt, but he must.6She doesnt need to be told. She
14、 has already known it.（客观情况使得告诉她没有必要：她已经知道）She neednt be told. We should keep it secret from her.（主观上不愿告诉）1. ought 没有词形变化，通用于所有人称，可以用于现在时，过去时和将来时，同带 to 的不定式连用，否定式为 ought not to (oughtnt)，疑问式把 ought 放在主语前。例如：He knew he ought not to tell her that.Note:ought to 与 must, have to, should 的含义比较接近，但不完全相同。ou
15、ght to 表示义务或责任，用以提醒某人注意其义务，或提出劝告，指出一个正确、明智的行为。must 强调的是主观愿望，指必须做什么，牵涉到说话人的权威。have to 则表示由某种情况、环境所迫而不得不做某事。should 同 ought to 用法完全相同，只是 ought to口气稍重一些。比较：You ought to respect the old.（劝告）You must do it at once.（含有说话人的权威性）Well have to reconsider the matter.（情况所迫：发现有新的问题）We should (ought to) do more for
16、 the country.（义务，责任）表示“必然”时，ought to 的语气不像 must 那么肯定。比较：This is where the gold deposits must be.这里一定是埋藏金子的地方。This is where the gold deposits ought to be.这里应是埋藏金子的地方。7used to +动词原形表示一种过去的习惯、过去的例行活动或方式，一个与现在情况相反的过去状况，意为“过去常常” ，否定式为 used not to (usednt to)，疑问式把 used 放在主语前。 be (become, get, grow) accust
17、omed /used to 动名词或名词（不能加动词原形）意为“习惯于，对习惯” 。例如：He usednt to like English, but he quite likes it now.The students soon got used to school regulations.She didnt use(d) to come.She usednt to come. 她过去不常来。Did he used to get up early?Used he to get up early? 他过去常早起吗？Didnt he used to get up early?Usednt he
18、to get up early? 他过去不是早起吗？Note:used to 还可以同 often, never, always 连用。例如：He often used to work late at night.他过去常工作到深夜。She always used to get up at four oclock in the morning.她过去总是早晨 4 点起床。除在一般将来时中用于第一人称外，shall 还有如下用法。1.表示征求意见或请求指示。例如：Shall we meet in the evening? 晚上见好吗？How shall I start the machine?
19、怎样开动这部机器？Note:shall 只表示“愿意按对方的指示去做” ，而 may, might 或 can 表示8“征求对方的同意” ，意为“行不行，好不好，可以不可以。 ”比较：Shall I come in? 你要我进来吗？May（或 might, can）I come in? 我可以进来吗？Shall I buy the dictionary? 要我买那本词典吗？May （或 might, can）I buy the dictionary?我可买那本词典吗？Shall I go there tomorrow? 要我明天去那里吗？May I go there tomorrow? 我明天
20、去那里好吗？用于第二、三人称，要重读，不可缩写、表示意图、意志、允诺、命令或必然结果等；但 shall 所表示的意志是说话人的意志，而非句子中主语的意志。在法律、条约、协定等文件中，shall 表示义务、规定等。例如：You shall have a lot of money= I shall give you a lot of money. （意图）你会有很多钱的。 （我会给你很多钱的）Each citizen shall carry his identification card when traveling.（规定）旅行时每个公民务必带上身份证、She shall get this pa
21、per in the evening.（允诺）He shall get what he deserves.（警告）Death is certain to all; all shall die. 物皆会死。 （命运）Better days shall soon follow.（预言）will 和 would 除在将来时态中用于第二、三人称外，还有如下用法。1. 表示请求（这时 will 和 would 通用，而 would 更委婉，也用wont） 。例如：9Will you give her the letter?你把这封信给她好吗？Would you please tell me your t
22、elephone number?请把你的电话号码告诉我好吗？2. 表示习惯或倾向。will 用于一般的习惯，would 用于描述过去的习惯或例行的活动。would 同 used to 强调过去的习惯性动作或状态，但如今已不存在，与现在的情况形成对比，既可表示过去持续的状态，也表示过去曾经的行为。例如：Scarf used to be heavy smoker.Father used not to be so forgetful.would 强调过去某种特定情况下的动作，是完全过去的事情，同现在没有联系。would 只表示重复的动作，不表示状态。比较：She used to get up at
23、six in the morning.（正，重复的行为）She would get up at six in the morning.（误）Man used to think that the earth was flat.（正，持续状态）Man would think that the earth was flat.（误）would 可以表示不规则的习惯，used to 则不可。例如：Sometimes she would take a walk in the neighboring woods.（不可用used to ）An Englishman will show you the way
24、 in the street.英国人在街上是会给你指路的。 （英国人一般都会这样做。 ）In those days, whenever I had difficulties, I would go to Mr. Lees for help.He used to get up at five, but now he gets up at six.10下面两句是错误的，应改用 used to:He would be very nervous when taking an exam.Before liberation, workers would work sixteen hours a day.3
25、. 表示推测。例如：It will be Mr. Wang knocking at the door.It would be about ten oclock when he left home.They will have arrived in New York by now.Note:will 表示推测时没有 must 把握大，should 也可以表示推测，但比will 把握略小。其程度由低到高为mightmay could should ought towouldwillmust。4. 表示命令、强迫等（只用 will，通用于所有人称） 。例如：All will arrive before 7:45.所有人员务必在 7:45 之前到达。I wont allow her to do that.我不会让她做那件事的。5. 表示意愿或固执坚持。用于非人主语时，表示固有性质、倾向。例如：She wont lend me the money.她不愿把钱借给我。He is the man who will go his own way.他是一个自行其是的人。The window wont open.窗子打不开。
