am is are的否定形式缩写

Be动词的否定

在 am ， is ， are ， was ， were 后面加not.

缩写式：am not ， isn’t ， aren’t ， wasn’t ， weren’t

1、 The man isn’t back. 主系表结构

2、 I am not back.

be动词根据主语决定时态，单复数

3、 They aren’t back.

4、 He wasn’t back.

5、 They weren’t back

Be动词提问和回答

Is he a teacher ?

Yes ， he is. / No ， he isn’t.

Are you a teacher?

Yes ， I am / No ， I am not.

Were they teachers?

Yes ， they were . / No ， they weren’t.