# Lesson 29 be 动词（肯定与否定）

### 1 be 动词的定义

be 动词是一个不规则动词，相当于中文里的"是"，通常有三种形态 am、is、are。它们的使用需要与句子主语的人称及单复数保持一致。

| 主语 | be 动词 |
| --- | --- |
| I | + am |
| He / She / It / 单数名词 / 不可数名词 | + is |
| We / You / They / 复数名词 | + are |

- The squirrel is orange. 这只松鼠是橙色的。
- The girls are best friends. 这两个女孩是好朋友。
- I am tired today. 我今天累了。

### 2 be 动词的肯定与缩写

在口语或非正式书写中，可以使用 be 动词的缩写形式。

| 肯定形式 | | | 缩写 | 例子 |
| --- | --- | --- | --- | --- |
| I | + | am | = I'm | I am / I'm a teacher. |
| He / She / It | + | is | = he's / she's / it's | It is / It's short. |
| We / You / They | + | are | = we're / you're / they're | We are / We're happy. |

### 3 be 动词的否定与缩写

be 动词的否定就是在 am、is、are 后加 not，否定形式也可以缩写。

| 否定形式 | | | 缩写 | 例子 |
| --- | --- | --- | --- | --- |
| I | + | am not | = I'm not | I am not / I'm not a student. |
| He / She / It | + | is not | = he's not / he isn't<br>= she's not / she isn't<br>= it's not / it isn't | She is not / isn't at home. |
| We / You / They | + | are not | = we're not / we aren't<br>= you're not / you aren't<br>= they're not / they aren't | They are not / aren't drawing. |

### 本课小结

| 人称 | be 动词 | 肯定与缩写 | 否定与缩写 |
| --- | --- | --- | --- |
| I | am | I'm | I'm not |
| He | | he's | he's not / he isn't |
| She | is | she's | she's not / she isn't |
| It | | it's | it's not / it isn't |
| We | | we're | we're not / we aren't |
| You | are | you're | you're not / you aren't |
| They | | they're | they're not / they aren't |

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