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Do：一个给力的助动词

和汉语不同，英语常用助动词 (auxiliary verbs) 来给主要动词进一步语义或语法信息。这里介绍一个常用、管用的助动词：do 。

Do 是个动词，可是放在命令或指示前面，do 变成一个有强调语气和敦促作用的助动词：

Do be good! （对孩子：要听话！）
Do be careful! （小心哦！）
Do come again! （再来哟！）

大家知道 Do come again! 和 Please come again! 两句子的区别吗？

这里举几个 do 的不同用法：

Do shut up, Michael, and get on with your homework.

Do write and let me know how you're getting on.

If I do come, I'll bring some food.

Customer: Can I buy stamps here?
Storekeeper: Well, we do sell them, but we haven't got any at the moment.

Visitor: May I have a look at your beautiful garden?
Host: Please do!
(Please do = please do have a look)

汉语虽然也有助动词（如"我去做"，"我要做"，"我会做"），但汉语的助动词通常不是明显表示的，而是从语气/语境领会出来的（"我做！"），这可能是为何中国人说英语时不习惯把 do 当助动词来用的一个原因吧？

顺便一提，英语还有这些其他助动词：

1． Jay may get a call from his son today.
2． I shall be there at 6.
3． She could be late coming.

上面句子 may, shall 和 could 都是助动词。