【Do第三人称单数】在英语语法中，“do”是一个非常常见的动词，通常用于构成一般现在时的疑问句和否定句。然而，当主语是第三人称单数（如he, she, it）时，"do"的使用需要进行变化。这种变化是英语语法中的一个重要知识点，尤其对初学者来说容易混淆。
为了帮助大家更好地理解“do”在第三人称单数中的用法，以下是对该语法点的总结，并通过表格形式进行清晰展示。
一、
在一般现在时中，当主语是第一人称（I, we）、第二人称（you）或复数第三人称（they）时，动词直接使用原形，如：I do, you do, they do。但当主语是第三人称单数（he, she, it）时，动词“do”需要变为“does”。
例如：
- He does his homework every day.
- She does not like coffee.
- Does she go to school by bus?
因此，“do”在第三人称单数中变成“does”，这是构成疑问句和否定句的关键变化。掌握这一规则有助于正确构建句子结构，避免语法错误。
二、表格对比
| 主语 | 肯定句 | 否定句 | 疑问句 |
| I | I do my homework | I do not do my homework | Do I do my homework? |
| You | You do your work | You do not do your work | Do you do your work? |
| We | We do our tasks | We do not do our tasks | Do we do our tasks? |
| They | They do their work | They do not do their work | Do they do their work? |
| He | He does his work | He does not do his work | Does he do his work? |
| She | She does her work | She does not do her work | Does she do her work? |
| It | It does its job | It does not do its job | Does it do its job? |
三、小贴士
- “Does” 是 “do” 的第三人称单数形式。
- 在疑问句中，无论主语是谁，都使用 “do/does” 放在句首。
- 在否定句中，使用 “do not/does not” 来表示否定。
掌握这些规则后，就能更自然地使用英语表达自己的意思，尤其是在日常交流和写作中。