一.概念:
   助动词是帮助主要动词构成各种时态,语态,语气以及否定或疑问结构的动词.助动词分为时态助动词和结构助动词两种.
二.相关知识点精讲:
  1. 助动词be的用法
1） be +现在分词，构成进行时态。例如：
They are having a meeting.　他们正在开会。
English is becoming more and more important. 英语现在越来越重要。
2）　be + 过去分词，构成被动语态。例如：
The window was broken by Tom..　窗户是汤姆打碎的。
English is taught throughout the world.　世界各地都教英语。
3） be + 动词不定式，可表示下列内容：
　    a. 表示最近、未来的计划或安排。例如：
　　  He is to go to New York next week..　他下周要去纽约。
　　  We are to teach the freshmen.　我们要教新生。
　　  说明： 这种用法也可以说成是一种将来时态表达法。
　    b. 表示命令。例如：
　　  You are to explain this.　对此你要做出解释。
　　  He is to come to the office this afternoon.　要他今天下午来办公室。
　    c.　征求意见。例如：
　　  How am I to answer him?　我该怎样答复他？
　　  Who is to go there?　谁该去那儿呢？
　    d. 表示相约、商定。例如：
　　  We are to meet at the school gate at seven tomorrow morning.　我们明天早晨7点在校门口集合。
2. 助动词have的用法
1）have +过去分词，构成完成时态。例如：
　　   He has left for London.　他已去了伦敦。
　　   By the end of last month, they had finished half of their work.　 上月未为止，他们已经完成工作的一半。
　　2）have + been +现在分词，构成完成进行时。例如：
　     I have been studying English for ten years. 我一直在学英语，已达十年之久。
　  3）have +been +过去分词，构成完成式被动语态。例如：
　     English has been taught in China for many years. 中国教英语已经多年。
3.助动词do 的用法
1）构成一般疑问句。例如：
　   Do you want to pass the CET?　你想通过大学英语测试吗？
　   Did you study German?　你们学过德语吗？
2）do + not 构成否定句。例如：
　   I do not want to be criticized.　 我不想挨批评。
　   He doesn't like to study.　他不想学习。
　   In the past, many students did not know the importance of English.　
过去，好多学生不知道英语的重要性。
3） 构成否定祈使句。例如：
　   Don't go there.　不要去那里。
　   Don't be so absent-minded.　不要这么心不在焉。
说明： 构成否定祈使句只用do，不用did和does。
4）放在动词原形前，加强该动词的语气。例如：
　   Do come to my birthday party.　一定来参加我的生日宴会。
　   I did go there.　我确实去那儿了。
　   I do miss you.　我确实想你。
5）用于倒装句。例如：
　   Never did I hear of such a thing.　 我从未听说过这样的事情。
　   Only when we begin our college life do we realize the importance of English. 进了大学以后，我们才认识到英语的重要性。
说明： 引导此类倒装句的副词有never, seldom, rarely, little, only, so, well等。
6）用作代动词。例如：
　   ---- Do you like Beijing?　--你喜欢北京吗？
　   ---- Yes, I do.　--是的，喜欢。（do用作代动词，代替like Beijing.）
　   He knows how to drive a car, doesn't he? 他知道如何开车，对吧？
4. 助动词shall和will的用法
　  shall和will作为助动词可以与动词原形一起构成一般将来时。例如：
　　　I shall study harder at English.　 我将更加努力地学习英语。
　　　He will go to Shanghai.　　他要去上海。
说明：在过去的语法中，语法学家说shall用于第一人称，will 只用于第二、第三人称。现在，尤其是在口语中，will常用于第一人称，但shall只用于第一人称，如用于第二、第三人称，就失去助动词的意义，已变为情态动词，试比较:
　  He shall come.　他必须来。（shall有命令的意味。）
　  He will come.　他要来。（will只与动词原形构成一般将来时。）
5.助动词should, would的用法
1）should无词义，只是shall的过去形式，与动词原形构成过去将来时，只用于第一人称。例如：
　   I telephoned him yesterday to ask what I should do next week. 我昨天给他打电话，问他我下周干什么。
　   比较："What shall I do next week?" I asked. "我下周干什么？"我问道。
　   可以说，shall变成间接引语时，变成了should。
2） would也无词义，是will的过去形式，与动词原形构成过去将来时，用于第二、第三人称。例如：
　　  He said he would come.　他说他要来。
比较："I will go," he said. 他说："我要去那儿。"变成间接引语，就成了He said he would come。原来的will变成would，go变成了come.。
6. 短语动词
　　动词加小品构成的起动词作用的短语叫短语动词。例如：
　　Turn off the radio.　把收音机关上。（turn off是短语动词）
　　短语动词的构成基本有下列几种：
1）动词+副词，如：black out；
2）动词+介词，如：look into；
3）动词+副词+介词，如：look forward to。构成短语动词的副词和介词都统称为小品词

直接引语和间接引语

直接引语是直接引述别人的原话，原话用有引号，而间接引语是引述别人的话，不用引号。间接引语在多数情况下构成宾语从句。直接引语改为间接引语时，引述动词是现在时，则间接引语中的动词、时间、时态的形式不变。例如：She says, “ I’ll never forget the moment变成间接引语为She says that she’ll never forget the moment.但是如引述动词为过去时，间接引语中的动词、时间、时态、地点、人称等一般要作相应的变化。遵循下列规律：

三要素。

我们要很好地掌握直接引语变间接引语这一语法项目，关键要掌握下列“三要素”。

要素一：陈述句的间接引语——连接词用that，在口语中可省略。引述动词用said, told, ,等。例如：

1)  He said: “I’ve left my book in my room.”→

He told me that he had left his book in his room.

2) She said: “He will be busy.”→

She said that he would be busy.

要素二： 疑问句的间接引语。一般疑问句后连接词用if或whether，而引述选择疑问句时只能用whether，引述动词用asked，没有间接引语的可以加一个间接宾语me, him等，例如：

         She said to Tom, “Can you help me?”→ 

    She asked Tom if /whether he could help her.

1)  She asked, “Is this book yours or his?”→

    She asked me whether that book was mine or his.

2) 特殊疑问句用原句中的疑问词作连接词，改为陈述语序。例如：

   The teacher asked, “how did you repair it?” →

   The teacher asked me how I had repaired it.

要素三：祈使句的间接引语——采用“动词+宾语+不定式”结构。

      told

即  asked  sb. (not) to do sth.

      ordered

      warned

注意：引语中的呼语可改成宾语。引语中的please 去掉，动词改为 ask 

1) The teacher said to the students, “Don’t waste your time.” →

    The teacher told the students not to waste their time.

2)  The mother said, “Tom, get up early, please.”→

The mother asked Tom to get up early.

 “五不变”

    在直接引语变间接引语时，还要注意以下五种不变的特殊情况。

1． 直接引语如果是客观真理，谚（习）语，变间接引语时时态不变。例如：

         The teacher said, “The earth goes round the sun.”→

The teacher said that the earth goes round the sun.

My father said, “Practice makes perfect.”→

My father said practice makes perfect.

2.  直接引语中被引述的部分是反复出现的，习惯性的动作或说话时情况仍然存在的，变间接引语时，时态保持不变，例如：

     The boy said to us, “ I usually get up at six every day.”→

            The boy told us he usually gets up at six every day.

            He said, “We are still students.’→

            He said they are still students.

3． 直接引语如果有明确的表示过去的时间状语，时态不变。例如：

   He said to me, “I was born in 1978.”→

   He told me that he was born in 1978.

   The engineer said, “I was at college in 1967.”→

   The engineer said he was at college in 1967.

4．直接引语中凡有When， since，while 引导的从句，在变为间接引语时，只改变主句时态，从句的时态不变。例如：

　　He said, “I have studied English since I was a boy.” →

He said he had studied English since he was a boy.

She said, “I read the book while I was waiting for a bus.→

She said she had read the book while she was waiting for a bus.

Mr. Green said to them, “Joe told me all about his story when he asked for a job.”→

Mr. Green told them Joe had told him all about his story when he asked for a job.

5．如果直接引语中引述部分含有insist, suggest, demand等引导的虚拟宾语从句，变间接引语时，引语中的主从句时态都不变。例如：

He said, “We insisted that she start immediately.→

He said they (had) insisted that she start immediately.

She said, “He demanded that the girl leave at once.”→

She said he demanded that the girl leave at once.

另外，如果说话人转述自己的话，人称则可不变. 例如：

I said to him, “I have finished it.”→I told him I had finished it.

如果就在当地转述, here不必变为there，come不必改为go，如果就在当天转述，则today, yesterday, tomorrow等状语也不必变化。例如：

She said to us, I’ll come here tomorrow.”→

She told us she would come here tomorrow.