do
1.do和did用来加强语势。例如：
- I do hope you will come. Do come.
- Do be quiet. I did hope you would come.
这两句里的do和did都该重读。注意do be只用在祈使语气里，I do be happy和He does be happy都不可以说。相当于I am happy和He is happy的强势式是I am happy和He is happy。那am和is都该印作斜体，或在下面加上一横线，读起来该重读。
I do hope you will come是I hope you will come的强势式。Do come是Come的强势式。Do be quiet是Be quiet的强势式，是一种强势的请求，略有不耐烦的含意，却并不是命令。I did hope you would come是I hoped you would come的强势式。否定的强势式在用词上跟非强势式没有不同，只是把那否定的词重读。例如：
- I do not think he will come.
I do not think he will come.(强势式， don't 重读)
2.用do或did加强语势有“确定”的意味，下面每组里的两句意思不同：
- Don't come.
Don't come.(强势式,don't重读) - I hope you wil come. (hope 重读,“我希望[不是想象、猜想、假定相信、恐惧等]你来。”)
I do hope you will come. (do 重读,“我的确希望你。”) - He wrote to me. (wrote重读,“他写信给我[不是来看我,打电话给我,或打电报给我]。”)
He did write to me. (did 重读,“他的确写信给我。”) - He did not (或 didn't) write to me.(write 重读,“他不曾写信给我[他是来看我的,打电话给我的,或打电报给我的。”)
He did not(或 didn't) write to me.(not 或 didn't重读,“他的确不
曾写信给我。”)
3.注意下面各句里的do和did：
- Never do（或did）I see him.
- Not a word do（或did）I ever say to him.
- Little do（或did）I know about him.
- Hardly do（或did）I know about him.
- Seldom do（或did）I see him.
- Rarely do（或did）I see him.
- Only on Sundays do（或did）I meet him.
- Well do（或did）I remember him.
注意：以上各句里的do和did虽然都是用来加重语气的，但习惯上并不重读。do和did都用在主语I的前面，而且不可省去。假使省去了，never，not a word，little，hardly，seldom，rarely，only on Sundays和well都不可用在句首，如Never do I see him该改作I never see him，Never did I see him该改作I never saw him。除了only和well以外，never等词都有否定性质。
4.He studies English as hard as I do Chinese里的do代表study。He studies English as hard as I do里的do代表study English。这两种用法都很普通。但该注意下面各点：
（1）do不可代表动词to be和表语，如He is as much interested as I am里的am不可改作do。
（2）do不可代表从被动语态里推想出来的动词，如不可说His essays are always written as carefully as I do mine，该把do改作write。
（3）do不可用在被动语态，现在分词或动名词，如不可说：
- His essays are always written as carefully as mine are done. （该把done删去或改作written）
- He always writes as carefully as I am doing. （该把doing改作writing）
- He always writes as carefully as I am in the habit of doing. （该把doing改作writing）
（4）He studies English as hard as I do里的do可以省去，但通常不省去，因为I是代词。He studies English as hard as his brother does里的does通常省去，因为brother是名词.
5.注意下面各句里的do so，do it，which...do和as...do：
- I did not write my essay yesterday, but shall do so tomorrow.
- I did not write my essay yesterday, but shall do it tomorrow.
- I wrote my essay in English yesterday, which I seldom do.
- I wrote my essay in English yesterday, as I seldom do.
第三句里的which和第四句里的as都指wrote my essay in English，也可以说指writing my essay in English。
注意上面各句里的write和wrote都属于主动语态。下面各句都不可说：
- My essay was not written yesterday, but I shall do so tomorrow.
- My essay was not written yesterday, but I shall do it tomorrow.
- My essay was written in English yesterday, which I seldom do.
- My essay was written in English yesterday, as I seldom do.
6.do so和do it可说意思相同。例如：I did not write my essay yesterday, but shall do so tomorrow. 和I did not write my essay yesterday, but shall do it tomorrow. do so不及do it明确，do it里的it明白指write my essay那一件事。比较下面两句：
- When he heard the knock, he stood up to open the door, but as he did so, the telephone rang.
- When he heard the knock, he locked the door. I do not know why he did it.
但第一句里的so也可以改作it，第二句里的it也可以改作so。
7.There is nothing to do是“没有事可做（闲着）”。There is nothing to be done是“没有办法”。
8.do for，do to和do with意思不同。例如：
- What have you done for him? （你为他做了什么？你怎样帮助了他？）
- What have you done to him? （你做了什么害他的事？）
- What have you done with him? （你怎样处理了他？）
What can I do for you? 是口头惯用语，直译作“我能够为你做什么？”就是“你来看我有什么事？”或（店员问顾客）“你要买什么？”
9.在疑问句和否定句里，助动词do往往和have用在一起。例如：
- Do you have bread for supper?
- I do not have many visitors.
这两句可以改作：
- Have you bread for supper?
- I have not many visitors.
但远不及用do的自然。
把助动词do和have用在一起，在美国比在英国普通。在英国通常用在习惯或经常发生的事情，不用在一时或永久的事情，如通常说：
- Do you have bread for supper?
- I do not have many visitors.
但不说：
- Do you have bread for supper this evening? （该说Have you bread for supper this evening?）
- I do not have many visitors today. （该说I have not many visitors today。）
也不说：
- Do you have brothers and sisters?
- I do not have a very strong heart.
但在美国没有这种限制。
上面所举的各句里的have都作“有”解，或有近乎“有”的意思。在have a look，have a chat，have a good time，have a rest，have an accident，have an engagement等表达方式里的have和那后面的名词习惯用在一起。例如：
- Did you have a look at the picture? （不作：Had you a look at the picture?）
- I did not have a chat with him. （不作：I had not a chat with him.）
- Did you have a good time at the top of the hill? （不作：Had you a good time at the top of the hill?）
- He did not have a rest till late at night. （不作：he had not a rest till late at night.）
同样地，该说Did you have your hair cut yesterday? 不该说Had you your hair cut yesterday? 该说I did not have my hair cut yesterday，不该说I had not my hair cut yesterday。
10.比较下面两句：
- I have not（或haven't）to go. （1.我不必去。2.我只得不去，我不可去。）
- I do not（或don't）have to go. （我不必去。）
第一句有两个不同的意思，但I haven't got to go只作“我不必去”解。第一句用在第二个意思里很不普通。
比较下面两句：
- I haven't (got) to go next Sunday. （一次）
- I don't have to go on Sundays. （经常）
11.do nothing but（或except），do anything but（或except）和do less than三种表达方式后面的不定式没有to。例如：
- He did nothing but（或except）laugh.
- He did not do anything but（或except）laugh.
- He could hardly do less than laugh.
在None of them did anything but（或except）laugh等句子里的不定式也没有to。
下面三句里wait and see前面的to可有可无：
- There was nothing（或little）for James to do but (to) wait and see.
- It was impossible for James to do otherwise than (to) wait and see.
- What is there to do but (to) wait and see?
12.have done（停止）和have done with（停止、完结）两习语都属于完成时态。事实上只有完成时态而没有其他时态。
have done后面有时不接什么，有时接动名词，如I have done和I have done writing。have done with后面接名词，或代词，或动名词。例如：I have done with the whole thing. I have done with it. 和I have done with writing. I have done writing和I have done with writing意思相同。
have done和have done with里的have有时改作动词to be。例如：I am done with the whole thing. I am done writing. 和I am done with writing. 用动词to be主要流行在美国、苏格兰和爱尔兰。
13.do away with和do away都作“除去”解，现在通常用do away with而不用do away。
14.make do（do是不定式）作“勉强过去”解，make do with作“靠着…勉强过去”解。例如：In those days of high prices before liberation we found it very hard to make do. 和As I had broken my pen, I had to make do with a pencil.
15.How do you do? 是习惯用语，但通常不说How do your parents do? 和How does your brother do? 等，却说How are your parents? 和How is your brother? 等。
