do既可以做实意动词又可以做助动词

根据不同的用法，do可以化身为五种不同形态，分别是do，does，did，doing和done。

1. do用于一般现在时

例句:I often do my homework in the evening.

2. does用于第三人称单数的一般现在时

例句:He does his lessons every day.

3. did用于一般过去时

例句:They did homework yesterday.

4. doing常用于现在进行时或者非谓语动词(暂时不提)

例句:He is doing his homework now.

5. done 常用于完成时，被动态或者非谓语动词(暂时不提)