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英语中完全用作助动词的有三组词：
（1）be, am, are, is, was, were, been, being
（2）have, has, had, having
（3）do, does, did
shall, will, should, would虽然也是助动词，但它们有时的作用却接近情态动词，即可以说是介于助动词与情态动词之间的词。它们的作用和can, may, must有很多相近之处。为了方便仍将它们放在本节当中。
be作助动词的用法：
be作助动词主要用来构成：
（1）各种进行时态：
Organisers were waiting for Guiness World Records to confirm the record. 目前，活动组织者正在等待吉尼斯世界纪录的确认。
She is trying to reach you. 她正设法和你联系。
Both of us are going to the show. 我们两人都准备去看演出。
Her heart was beating violently. 她的心在猛烈地跳动。
I'll be here. I'll be helping them. 我将在这里，我将帮助他们。
They were hunting for jobs. 他们在找工作。
What have you been doing since then? 那以后你一直在干什么？
I thought you would be arguing about it. 我还以为你们会为此争论的。
（2）各种被动语态及被动形式：
Smoking is not permitted here. 这里禁止吸烟。
You are requested to be present at the ceremony. 请参加这场典礼。
I' m supposed to arrive at 2. 我应在两点到达。
He was fined $200. 他被罚款200美元。
They were shown round the city. 他们被带着在城里观光。
The goods will be shipped to you by train. 货物将由火车运到你处。
The case is (was) being investigated. 案件正在调查之中。
He said these people should be punished. 他说这些人应受到惩罚。
He asked to be forgiven. 他请求被原谅。
I walked fast to avoid being overtaken. 我走得很快，以免被人赶上。
be一般不能用于进行时，但可以用进行时表示一时的表现：
Don't talk rot. I' m being serious. 别瞎扯了，我是说正经的。
My dear child, you' re being childish. 我的乖孩子，你这是孩子气。
Am I being over-enthusiastic? 我这样是不是过度热情了？
He was being terribly friendly to Aunt Ruth. 他对鲁思阿姨特别友好。
be作实义动词（表示动作）的用法：
How long ago was it (=did it happen)? 这是什么时候的事了？
The party will be (=take place) in a week. 晚会一周后举行。
When is the wedding to be ? 婚礼什么时候举行？
They think that such a thing cannot be . 他们认为这样的事不可能（发生）。
be+不定式结构，这种结构可以表示：
（1）按计划、安排要发生的事或打算做的事（接近be going to）：
I am to see him today at six o'clock. 我今天六点钟和他见面。
The book I edited is to appear soon. 我编的那本书不久即将出版。
She was to meet Kurt at an agreed place on the street.她将在街上一个约定的地方和库尔特见面。
（2）该做或不该做的事（接近should, must, ought to, have to，等等）：
What am I to do (=What should I do) then? 那么我该怎么办？
In future you are not to go out alone. 以后你不要一个人出去。
Such men are to be pitied rather than despised. 这种人不应被看不起，而应当被同情。
（3）能或不能发生的事（接近can, may）：
How am I to pay such a debt? 我怎么还得起这么一笔债？
Not a cloud was to be seen . 天空上看不到一片云彩。
We are not to be bullied . 我们是不能被欺侮的。
（4）将来必然发生的事：
The worst is still to come . 最坏的情况还在后头。
They said goodbye, little knowing that they were never to meet again.他们道别了，完全不知道他们再也不会见面。
He didn't know that he was to become famous later on. 他不知道他将来会出名。
（5）（用在条件句中）如果想……：
If we are to be there in time, we'll have to hurry up.如果我们想及时赶到，我们得加紧赶路。
If I were to do that, what would you say? 如果我来做这事，你觉得怎么样？
还可和不定式的完成形式一道用，表示“本来打算……”：
I was to have seen him last Wednesday, but he did not come.我本来要在上星期三和他见面的，但他没有来。
We were to have been married last year. 我们本来打算去年结婚的。
have been结构，主要用来构成现在完成时：
It has been cold lately. 最近天很冷。
也可用来构成将来完成时：
If China can solve these issues, then the primary incentives to emigrate will have been taken away. 如果中国能够解决这些问题，那么移民的主要驱动因素将不复存在。
By tomorrow, I will have been a teacher for ten years. 到明天，我当教师就满10年了。
还可用作完成进行时或用于被动语态：
The boxer has been training very hard. 这个拳击运动员一直在抓紧练习。
They have been travelling for a whole year. 他们整年一直在旅游。
He has been nominated for president. 他被提名为总统候选人。
I' ve been assigned to cover international news. 我被派采访国际新闻。
have been to表示“到过（某地方）”：
Have you ever been to Japan? 你到过日本吗？
（比较：Has he gone to Japan? 他到日本去了吗？）
How many countries have you been to ? 你到过多少国家？
She' s just been to a party. 她刚参加一个晚会回来。
在和副词连用时，to要去掉：
Where have you been ? 你到哪儿去了？
He' s only been there two or three times. 他只到过那里两三次。
Who has been here? 刚才谁在这里？
后面有时跟不定式，表示“去做某事”：
I' ve been to see your grandmother. 我（刚才）看你奶奶去了。
I' ve been three times to see her. 我去看过她三次了。
有时跟介词短语：
Have you ever been on holiday in winter? 你曾冬季出去度过假吗？
I' ve never been for a swim at night. 我从未在夜间游过泳。
have作助动词的用法：
have作助动词主要用来构成各种完成时态或完成进行时态：
You haven't been abroad before, have you? 你没出过国，对吧？
What have you been doing since then? 从那时起你一直在干什么？
I had not been reading for half an hour when I heard steps outside.我看书还不到半小时就听见外面有脚步声。
She' ll have arrived in Shanghai by 3 o'clock. 三点前，她就可以抵达上海。
I was afraid she would have left for home when I got there. 我担心到达那里时，她已经回家了。
还可构成不定式、动名词、现在分词的完成形式：
You ought to have noticed it. 你应当已经注意到这件事。
I'm sorry to have given you so much trouble. 对不起，给你带来这么多麻烦。
I remember having heard you speak on that subject. 我记得曾听见你谈过这个问题。
Pile was apologizing to Helen for having kept her waiting.派尔正为让海伦久等而向她致歉。
Having been there once, she knew the place quite well.由于去过一次，她对这地方很熟悉。
have作实义动词的用法：
（1）表示所有关系：
He had an American accent. 他有美国口音。
Bad news has wings. 坏消息传得快。（谚语）
（2）和许多名词（特别是与动词同形的名词）连用，表示一个动作：
Daddy and I had a long talk this afternoon. 爸爸和我今天下午谈了很长时间。
Let's have a look at these things. 咱们看看这些东西。
I must have a wash first. 我得先洗一洗。
She had a swim every day. 她每天游一会儿泳。
He had not for ten years had a quarrel with anyone. 10年来他从未和任何人吵过架。
（3）表示“吃”“喝”“抽烟”“患（病）”等：
Lanny had his meals in the hotel dining room. 兰尼在旅馆的餐厅吃饭。
Everybody here has the influenza . 这儿人人都患流感。
Wilson had a severe headache that evening. 那天晚上威尔逊头疼得厉害。
（4）带复合宾语的结构：
① 跟不带to的不定式结构，表示“让某人做某事”：
He did not wish to have her go with him. 他不愿让她和他一起去。
I will not have you worry her. 我不能让你给她烦恼。
② 跟带过去分词的结构，表示“让某事做好”“遭到某种情况”等：
She might have gone to have her hair waved . 她可能去烫发去了。
She is having her eyes tested . 她将要去检查视力。
③ 跟带现在分词的结构，表示让某种情况发生：
He soon had them all laughing . 他很快逗得大家都笑了。
We'll soon have you walking about again. 我们不久就可再让你到处走动了。
（5）have to的用法
have to表示“不得不”：
We have to go to a meeting now. 我们现在得去开会了。
He may have to cancel the plan. 他可能需要取消这个计划。
have got to也有同样意思：
I' ve got to be off now. 我现在得走了。
The child has got to have an operation. 这孩子必须得动手术。
（6）have got（=have）的用法：
I' ve got another three minutes. 我还有三分钟。
I haven't got a thermometer. 我没有体温表。
do作助动词时，有三种用法：
（1）用在一般现在时及一般过去时中，构成疑问句、否定句或倒装句：
When do we meet again? 我们什么时候再见面？
I don't care what she thinks. 她怎么想，我不管。
Never did I see him again. 后来我再也没见到过他了。
I don't often go to the theatre, neither does she. 我不常去看戏，她也不常去。
（2）加在动词前，表示强调：
I do hope you'll stay for lunch. 我的确希望你留下吃午饭。
Please! Do be quiet a moment! 求求你们！安静一会儿！
（3）用来表示刚提到的动作，以避免重复：
Nancy works 16 hours a day. I don't know how she does it.南希每天工作16小时，我不知道她怎么做到的。
“May I come round in the morning?”“Yes, please do .”“我早上来行吗？”“行，请早上来吧。”
do作及物动词，主要有下面用法：
（1）和一个名词（代词）连用表示“做（某事）”：
I used to do business with them. 我过去常和他们做生意。
Alison and I did our homework together. 艾利森和我一道做作业。
可用于被动结构：
Easier said than done . 说来容易做时难。（谚语）
Well begun is half done . 头开得好，事成一半。（谚语）
（2）和动名词连用：
Martin did no reading that night. 马丁那天晚上没看书。
Maria did most of the talking . 大部分时间都是玛丽亚在讲话。
（3）和一个名词连用，表示“打扫”“洗”“刷”“煮”“学”等：
They do the kitchen and bathrooms every day. 他们每天打扫厨房和浴室。
I am doing the dishes . 我在洗盘子。
（4）还可表示“写”“画”等：
Martin has done an excellent article . 马丁写了一篇精彩的文章。
She did some pretty sketches . 她画了几张漂亮的素描。
（5）表示“招待”“对待”“扮演”“欺骗”等：
They did me very well at that hotel. 在那家旅馆他们把我招待得很好。
Who's doing Ophelia? 谁扮演奥费丽娅？
That shopkeeper did me. 那家商店的老板骗了我。
do作不及物动词的用法：
（1）表示工作、学习等方面的情况：
He did very well in the examination. 他考得很好。
Everything in the garden is doing well. 花园里所有花木都生长良好。
（2）表示“行”“够了”“合适”“可以”等：
Will it do if we let you have an answer by Friday?我们星期五以前给你答复行吗？
No, that won't do . It's too risky. 不，那不行，太冒险。
Will £5 do ? 五英镑够吗？
用于将来时态（用于各种人称）：
I must go; the students will be waiting for me. 我得走了，学生们会等我的。
用于第二人称后构成问句，表示“请求”：
Will you have a whisky, Doctor? 大夫，你要不要喝一杯威士忌？
If you want help, let me know, will you ? 如果你需要帮助，告诉我，好吗？
有时接近祈使句，但口气比较温和：
Bring the fruit up to the dining room, will you ? 把水果送到楼上餐厅里来，好吗？
Will you please, at once, pack up and leave? 请马上收拾行李离开。
有时用否定式，可译为“可否”“要不要”：
Won't you take off your coat? 你要不要把大衣脱掉？
Won't you come in and have something to drink? 你要不要进来喝点什么？
I meant to reason with you, but you won't reason. 我本想和你讲道理，但你不肯讲道理。
用于各种人称表示：
（1）习惯：
Boys will be boys. 男孩子总是男孩子。
Oil and water will not mix. 油和水混不起来。
These things will happen. 这种事总是要发生的。
（2）决心：
“Tell me the secret.” “I won't .”“把秘密告诉我。”“我才不哩。”
We will never talk about that subject again. 我们绝不再谈这个问题。
（3）诺言：
I won't let you down in any way. 我绝不会做对不起你的事。
We' ll pay back the money soon. 我们不久就偿还这笔钱。
（4）命令、叮嘱：
You will not go out today; instead, you will stay in and work.今天你不要出去，相反，你要待在家里干活。
No one will leave the examination room before 12 o'clock. 12点前谁也不准离开考场。
（5）猜测：
This will be the house you're looking for. 这想必是你找的房子。
The audience will not be aware of such detail. 听众们想必不知道这样的细节。
would作助动词时，可用来构成过去将来时（可用于各种人称）：
I thought you would be sleeping . 我还以为你会在睡觉呢。
用来客气地提出请求、愿望、看法等（比用will更客气一些）：
I would hate to move to another house now. 我不想现在搬到别处去。
I wouldn't mind being a messenger. 我不介意做一个传书递简的人。
If he were in town he would help you. 如果他在城里，他会帮助你的。
If you had taken my advice, this wouldn't have happened .如果你听了我的劝告，这事就不会发生了。
She would have said more, had he not walked away.如果他没走开，她还会多说一些的。
还可用于含蓄条件句中：
Denial would have been useless. 否认是没有用的。
But for your help we would have been late . 幸亏你帮忙，要不我们就迟到了。
Such a thing wouldn't have happened elsewhere. 这样的事在别处是不会发生的。
可用在虚拟条件句的从句中：
If Ann would admit this I'd be quite happy. 如果安肯承认这一点，我会很高兴。
If they would put their heads together, they would find ways to tide over the difficulty.如果他们肯集思广益，他们会找到渡过难关的办法。
有时表示“倾向”（will的过去式）：
The windows wouldn't open . 窗子打不开了。
The wound would not heal . 伤口老不愈合。
用于would rather (sooner) 等结构中：
He would rather listen to others than talk himself. 他宁愿听别人谈而不自己谈。
We would sooner ( rather ) have left on the 8th. 我们宁愿8号走。
I would as soon stay at home. 我宁愿待在家里。
后面有时跟从句：
I'd rather ( sooner ) you didn't ask me to speak. 我宁愿你不让我发言。
I'd rather you knew that now, than afterwards. 我宁愿你现在知道而不是以后知道。
作助动词的用法：
主要用于第一人称，构成将来时态，特别是在疑问句中，用以征求对方意见：
We shall be going away tomorrow by an early tram. 我们明天将坐早车离开此地。
Tomorrow we shall have finished with this business. 明天我们就能干完此事。
现在，在陈述句中用shall的时候越来越少。美国人都用will，英国人也多用will。shall not可紧缩为shan't /Fɑ:nt/，美国人读作/FAnt/：
I shan't be long. 我不会去太久。
We shan't be coming back today. 我们今天不回来了。
在英国可用于各种人称，表示：
（1）许诺：
You shall hear everything directly you come. 你一来就可听到所有情况了。
I don't want to be hard on him; he shan't be pressed . 我不会对他苛刻，不会逼他。
（2）决心：
I shan't go back there. 我绝不回那里去。
That day shall come . 那一天一定会来。
Terrorism shall not pass. 恐怖主义不能逍遥法外。
（3）威胁、命令：
He shall suffer for this. 他将为此受苦。
She shall do as she is told. 她得按命令行事。
He shan't come here. 我不会让他来。
（4）规定：
Each competitor shall wear a number. 每个参赛者要戴一个号码。
Members shall enter the names of their guests in the book provided.会员必须将他们客人的名字登记在提供的本子里。
All foreign residents shall have reported to the nearest police station by September 20.所有外籍居民必须于9月20日前到最近的派出所去一趟。
（5）表示“应当”（和should的意思差不多）：
We demand that the rich shall pay for this. 我们要求富人为此付款。
It has been decided that he shall be given the job. 已决定应当给他这份工作。
这类用法已不很普遍，在很多情况下都可用will代替，尤其在美国。
作助动词：
should是shall的过去式，用来构成过去将来时（用于第一人称，然而现在一般都用would，特别是在口语中）：
We thought we should never see you again. 我们以为会再也见不到你了。
The BBC weather report this morning said that we should have rain.
英国广播公司天气预报说今天有雨。
用在某些从句甚至主句中，表示惊异、不以为然等情绪：
I can't think why he should have said that. 我想不明白为什么他竟说出这样的话。
It is odd that they should not have presented you with a copy.他们竟然没有送你一本，真太奇怪了。
用在虚拟条件句中，有下面几种情况：
（1）用在主句中（这时用would的人更多，不分人称，但第一人称后仍有人用should）：
I should never have done it if I hadn't been so hard up.要不是我经济上那样困难，我绝不会做这事。
I should not have laughed if I had thought you were serious.要是我以为你是认真的，我就不会发笑了。
（2）用在含蓄条件句中（用于第一人称，但更多人用would）：
We shouldn't have won without you. 要不是有你，我们不会赢。
What should I have done in her place? 我要是处在她的地位，我会怎样做？
（3）用在条件从句中，表示未来情况（主句可用陈述语气或祈使语气）：
I should be happy to go with you if I should not be in the way.如果我不碍事，我愿和你们一道去。
Should I be free tomorrow, I will come. 如果明天我有空我就来。
用在so that，lest等引导的从句中：
We hid it so that he should not see it. 我们把它藏起来，以免他看到。
He offered to write it out for her, lest she should forget .他提出替她写下来，以防她忘记。
can表示现在或将来的情况，主要表示：
能力（能做某事）：
Two eyes can see more than one. 两只眼睛比一只看得清。（谚语）
His sprawling impact on science can't be reduced to such concise phrases. 他对科学广泛的影响无法用如此简短的句子概括。
be able to可表示同样意思：
Look! I can/am able to stand on my hands! 瞧！我能倒立！
Can you/ Are you able to speak a foreign language? 你能讲外语吗？
can只能表示现在情况，没有完成形式，而be able to则可以：
I haven't been able to sleep recently. 最近，我睡不着觉。
可能性（可以，可能）：
So data of this kind can be valuable. 因此，这样的资料有时很有价值。
同意，允许（可以）：
You can ' t smoke here. 你不能在这里抽烟。
在这里，can和may意思差不多。在日常口语中用can时更多。
用在疑问句及否定句中，表示惊讶、不相信等：
How can you be so conceited? 你怎么能这样高傲？
Can he still be alive after all these years? 过了这么多年，他还活着？
后面有时跟完成形式或进行形式：
You can't have forgotten me. 你不可能已忘记我了。
They can't have gone out because the light's on.他们不可能出去了，因为灯还亮着。
What on earth can she be doing ? 她此刻能在干什么呢？
作为can的过去式，表示过去情况：
（1）能力：
She could sing very well when she was a girl. 她小时候歌唱得很好。
She couldn't understand his state of mind. 她不能理解他的心态。
这时可以用was (were) able to表示同样的意思：
But several seconds after the launch the rocket blew up, before the new second stage motor was able to ignite. 在发射数秒后，第二级新助推器点燃之前，火箭发生了爆炸。
She wasn't able to ( couldn't ) answer the question. 她不能回答这个问题。
（2）可能性（可以、可能）：
It was so dark that we could see nothing. 天那么黑，我们什么也看不见。
Mary could be pretty naughty when she was a child. 玛丽小时候有时很调皮。
用来代替can，意为：
（1）委婉地提出请求、想法等：
I could come early, if necessary. 如果有必要，我可以早点儿来。
I couldn't be happier. 我再高兴不过了。
（2）用于疑问句及否定句，表示惊异、不相信等：
Could this be true? 这能是真的吗？
They couldn't have left so soon. 他们不可能走得这么早。
用于虚拟条件句：
If it hadn't been for the freezing wind they could have reached the injured man in time. 要不是有刺骨的寒风，他们就及时赶到伤员身边了。
也可用于含蓄条件句中：
Why didn't you apply for the job? You could have got it.你干吗没去申请这份工作？你是有可能得到这份工作的。
Paul couldn't have gone anyway because he was ill.保罗不管怎样都不能去，因为他生病了。
“could+完成形式”可用来谈过去情况：
（1）表示那时“（不）可能”，代替can的过去式：
We could not have heard them because of the noise from the river.由于有河水声，我们不可能听见他们的话。
I do not see how I could have done otherwise.我看不出那时我还能有什么别的做法。
（2）表示那时“本来可以”“差点儿就要”等：
I could have lent you the money. Why didn't you ask me?我本来可以借这笔钱给你的。你为什么不向我提出？
Indications are that the accident could have been prevented.迹象表明，这次事故本来是可以避免的。
（3）用来提出委婉的批评：
You could have been more considerate. 你本可考虑得更周到的。
You could have started a little earlier. 你本可早点儿动身的。
用来提出问题（问可不可以）：
May I have the key? 能把钥匙给我吗？
You may do exactly as you like. 你可以爱怎么做就怎么做。
If I may say so, your work needed revision.如果我可以这样说的话，你的著作需要修订。
用在陈述句中表示“允许”（表示“可以”，有“允许”的意味）：
People may not pick flowers in the park. 人们不得在公园里攀折花木。
Dogs may not be taken into these carriages. 不得带狗进入这些车厢。
用在陈述句中表示“可能”：
He may be engaged. 他可能有事。
It may be a new species. 它可能是一个新品种。
后面可以跟完成形式或进行式：
You may have read some account of the matter. 你可能已看到对这事的一些报道。
She may be bringing a few friends home. 她可能会带几个朋友到家里来。
He may not have been feeling well. 他可能身子不舒服。
可以和well连用，表示“很可能”：
That may well have been their intention. 这很可能是他们的意图。
It may well be the largest cathedral in the world. 它很可能是世界上最大的教堂。
用来表示祝愿：
May some of the suggestions prove of value to you! 愿这些建议有些能对你有益！
用于may as well，意为“不妨”：
If that is the case, I may as well try . 既然如此，我不妨试一试。
Since (Now) you are here, you may as well make yourself useful.既然你在这儿，不妨做点有益的事。
用作may的过去式：
（1）表示“可以”：
I asked if I might glance through the exercises. 我问可否看看这些练习。
He suggested one or two books which they might buy . 他推荐了一两本他们可以买的书。
（2）表示“可能”：
With careful modulation, aging might be reversed . 通过小心谨慎的调节，衰老的过程可能逆转。
I was careful not to look at him. He might have seen the surprise in my eyes.我注意不看他。（否则）他可能会看出我惊异的眼神。
（3）用在某些状语从句中：
I wished that you were there so that I might thank you in person.我希望你在那儿以便我能当面向你致谢。
Amy was not allowed to go to bed, lest she might be needed .他们不让埃米睡觉，以防需要她。
用来代替may，谈现在的情况，口气比may更委婉些：
（1）表示“可以”（用may时可能更多一些）：
Might I inquire if you are the owner? 我可否问一句你是不是老板？
You might just give me half a cup. 你给我半杯就行了。
（2）表示“可能”“或许”，比用may所表达的可能性更小一些：
She might have been taken ill quite suddenly. 她或许是突然生病了。
I might have come to a wrong conclusion. 我可能得出了错误的结论。
might well可表示“很可能”：
You might well be right. 你很可能是对的。
用在虚拟条件句中：
If it hadn't been for Margaret, I might not have understood. 要不是马格雷特，我或许还不能理解。
还可用在含蓄条件句中：
I still think I might have made a go at it.我仍然认为我可以试一试的。
用来表示轻微的埋怨或批评：
You might have let me know before! 你要是早点儿让我知道就好了！
用“might+完成形式”谈过去的情况，意为“或许……”“本来可以”，即“本来或许可以的，但事实已不可能了”：
Father mightn't have been to blame. 或许不可能怨父亲。
用于might as well（和may as well意思相同，表示“不妨”）：
I'm ready, so I might as well go now 我已准备好，因此不妨现在就走。
A lot of men died who might have been saved . 很多人本来可以获救的，却死了。
有时可表示“还不如”：
We might as well have gone ( go ) home as you suggested.我们还不如照你说的回家去。
表示“必须”“一定要”“得”（多指现在或将来情况）：
可用于被动结构，也可用于进行形式：
A work ill done must be done twice. 一件作品没做好必须重做。（谚语）
must也可用来表示过去情况，但用had to也许更清楚一些：
Why did you have to go there? 你为什么得去那里？（这样时间比较清楚）
She asked her boss if she must ( had to ) work overtime.她问老板她是否一定要加班。
mustn't表示一定不要：
Of course she mustn ' t leave us.当然她不能离开我们。
mustn't意为“千万不要”。但在回答以must引导的问题时，若是否定回答，不要说mustn't（绝不要），而要用needn't（不需要）：
“Must I come at four?”“Yes, you must.”
“我一定要四点钟来吗？”“是的，一定要四点来。”（“No, you needn't. You may come any time in the afternoon.”“不一定，你可以下午任何时候来。”）
表示“一定是”“准是”，即有“揣度”“估计”的意味：
Judging by the smell, the food must be good. 从香味上看，这菜一定很好吃。
Your brother must be anxious to know the particulars. 你哥哥一定急于知道详细情况。
后面可跟完成形式或进行形式，表示“估计已经”或“估计正在”：
Nonsense, you must have misheard . 胡说，你准是听错了。
You must be joking . 你准是在说笑话。
Someone must have been smoking here. 一定有人一直在这里抽烟。
表示“偏要”“偏偏”（做可能发生不愉快的事）：
Why must she be so nasty to me? 为什么她偏对我这么恶劣？
ought总与to连用，表示：
（按道理）应该，应当（意思接近should）：
One (A fellow) ought to be broad-minded about things.
对事情，一个人应当宽宏大量。
可用于被动结构：
He ought to be isolated . 他应当被隔离。
后面可跟不定式的完成形式或进行形式：
I ought to have helped her, but I never could. 我本该帮助她的，却从未能这样做。
一种揣测（想必应当已经）：
Jim ought to be up now. 吉姆现在应当已经起床了。
后面可以跟完成形式或进行形式：
He ought to have arrived by now. 现在他应当已经到了。
We ought to be hearing from him soon. 我们不久应当会接到他的信。
need作情态动词的用法：
need用作情态动词主要用在否定句中，表示“不必”：
You needn't clean the windows. They aren't dirty. 你不必擦窗子，不脏。
“Must we take action immediately?”“No, you needn't fuss .” “我们必须立即采取行动吗？”“不，你不必大惊小怪。”
可用于被动结构，后面也可跟完成形式：
They need not have been punished so severely. 他们不必受到这样严厉的惩罚。
也可以用于下面这类有否定意思的句子：
I don't think you need take it too seriously. 我看你不必对这事太认真。
I don't see why we need discuss it further. 我看不出我们还有什么必要进一步谈。
用于疑问句：
Why need you go today? 为什么你需要今天走？
Need you have scolded him so severely? 你有必要这样严厉地批评他吗？
可用在表示疑问的从句中：
Do you think you need tell her about it? 你认为你有必要告诉她这件事吗？
I wonder if I need bring my mosquito-net. 不知我有否必要带蚊帐。
情态动词need的否定式是needn't,及物动词need的否定式是don't/doesn't/didn't need。
作及物动词的用法：
作为及物动词，need表示“需要”，后面可以跟：
（1）名词或代词：
Humans need glucose to survive. 人类需要葡萄糖才能生存。
I don't need anything. 我什么也不需要。
（2）不定式：
They need to tackle the problem in a new way. 他们需要以新的方式处理这个问题。
The house needs to be redecorated. 房子需要装修。
（3）动名词（有被动意思，相当于不定式的被动形式）：
The pants need pressing (to be pressed). 裤子需要熨烫。
The garden needs watering. 花园需要浇水了。
（4）复合结构：
I need you over to help me with the children. 我需要你过来帮我看孩子。
I need this tooth out. 我需要拔掉这颗牙。
作情态动词的用法：
作情态动词时表示“敢”，这时没有人称形式，但可有过去式dared，主要用于：
（1）否定句：
He daren't ask his boss for a day off. 他不敢向老板请求休一天假。
I scarcely dare think of it. 我简直不敢想这事。
（2）疑问句：
How dare you say I am a liar? 你竟（怎么）敢说我是个撒谎的人？
Dare you ask him? 你敢问他吗？
How dare he take my bicycle without even asking?他怎么敢骑走我的自行车也不说一声？
dare偶尔还可用于肯定句中：
I wonder if she dared come home. 不知她敢不敢回家。
（3）dare say（猜测，或许，可能）：
I dare say I overdo it. But you go to the other extreme. 或许我做得过分，但你却走了另一个极端。
You're tired, I dare say . 或许你累了。
作及物动词的用法：
作及物动词时可以与一些助动词如do, would, won't, have等连用：
（1）表示“敢”（做某事）（可用于各类句子）：
She dared to walk the tightrope without a net. 她敢于不用安全网踩钢丝。
He dares to accuse me of dishonesty. 他（竟）敢说我不老实。
有时甚至不带to：
Sally is the only person in our class who dares (to) answer our teacher back. 萨莉是我们班上唯一敢和老师顶嘴的人。
（2）表示“敢于面对”或“尝试”：
The actress dared a new way of playing that famous character.那位女演员敢于尝试以一个新方式来扮演这个著名角色。
（3）表示“向……挑战”“要某人做某件危险的事”：
I dared him to fight. 我要求和他打一架。
I dare you to jump off that wall. 我看你敢不敢从墙上跳下来。
be able to常和动词一起用，表示“能够”，意思接近can，有时两者可以换用：
I' m not able to (can't) explain this. 我不能解释这个问题。
He was able to (could) speak five languages. 他能讲五种语言。
但be able to可用于许多时态，这时可能无法换为can, could：
I haven't been able to get in touch with her. 我一直未能和她联系上。
She had been able to send money home regularly to maintain the family.她一直能定期寄钱回家维持家人的生活。
Each drone would be able to deliver enough supplies to feed up to 50 people per day.每架无人机运载的物资能满足50人一天的消耗。
be able to还可和情态动词或某些系动词连用：
I ought to be able to live on my salary. 我应当可以靠薪水生活。
You might be able to persuade him. 你或许能劝说他。
She should be able to give us a good answer.她应当可以给我们一个令人满意的答复。
He seemed able to put complicated thought in simple words.他似乎能用简单的词表达复杂的思想。
还可以用于非谓语动词中：
He said he so much regretted not being able to swim .他说他对不会游泳感到非常遗憾。
She grasped my hand, not being able to say anything.她抓住我的手，一句话也说不出来。
have to的意思接近must（must强调说话人的意愿），而have to表示客观上的必要，常可译为“（不）得（不）”，否定式表示“不必”：
You must come with us. 你一定要和我们一道去。
I had to go to hospital. 我得去医院。
You have to have a social-media presence if you want to have a successful business. 如果你想把事业做成功，就得在社交媒体上有影响力。
have to可用于各种时态：
We failed to catch the bus. We had to walk home. 我们没赶上车，只好步行回家。
If it hadn't been for her support, he would have had to leave .如果不是她支持，他就不得不离职了。
have to还可和情态动词一起用：
He may have to cancel his plan. 他可能不得不取消他的计划。
They might have to ask his permission to do this.他们这样做可能不得不征求他的同意。
have to的疑问句及否定句都借助do(es)，did构成：
What do I have to do to get a license? 我要怎样做才能领到驾驶证？
She doesn't have to stay up so late. 她不必熬夜到这么晚。
have got to和have to的意思差不多，也可译为“不得不”“一定得”：
It's the one thing you' ve got to be careful about. 这是你必须小心处理的一件事。
Have you got to get yourself involved with all this? 你有必要卷进这一切吗？
had better也接近一个情态动词，和should的意思很相近，表示“最好”；had常紧缩为“d”：
Graduates had better known what they want before they start looking for a job. 毕业生最好在求职前想清楚自己想要什么。
You had much better have the thing out at once. 你最好马上把事情谈清楚。
后面有时可跟进行式，表示立即做某事：
I think I' d better be going . 我想我最好还是马上走。
You' d better be getting your clothes ready. 你最好马上把衣服准备好。
had有时可省略：
You better stop arguing. 你们最好不要争论了。
Better not wait for them. 最好别等他们了。
Better get his file then. 最好把他的档案取来。
had best也有类似的意思：
I thought I had best have your opinion first. 我想最好先听你的意见。
You had best get home before midnight. 你最好在午夜之前回到家里。
used to表示“过去（常常）……”（现在已不再如此）：
I used to play tennis a lot but I don't play very often now.我过去常常打网球，但现在不常打了。
He used to be devoted to her. 他过去是很爱她的。
它的疑问结构和否定结构通常由助动词did构成：
Did you use to eat a lot of sweets when you were a child? 你小时候吃很多糖吗？
I didn't use to have my own room. 我过去不是一个人住一间房的。
有时也有人用下面形式：
Used you to know them? 你过去认识他们吗？
She used not to be so forgetful. 她过去不是那样爱忘事的。