肯定句改否定句可大致分为三类：

01

有be动词或者情态动词的肯定句变否定句

转换方法：

在be动词或情态动词后面直接加 not

肯：I am a teacher.

否：I am not a teacher.

肯：He can play the guitar.

否：He can not play the guitar.

02

有实意动词(表示动作的动词)的肯定句变否定句

①当句中的动词是原形时，加don't。

肯：I have dinner.

否：I do not have dinner.

②当句中的动词是第三人称单数时，加doesn't ，再加动词原形。

肯：She likes bread.

否：She doesn’t like bread.

③当句中的动词是过去式时，用didn't，加动词原形

肯：We had a great time during our holiday.

否：We didn’t have a great time during our holiday.

这里有个口诀可以帮助大家牢记以上的变化规则：

有be，be 后加not

有情，情后加not

无be 无情， 借助动词后加not

03

含有动词have/has的肯定句变否定句

①当have表示“某人有什么的时候”，其否定形式为have not/has not

肯：I have two books.

否：I have not two books.

②当have作为实意动词时，其否定形式为 do not have/does not have

肯：He has lunch .

否：He does not have dinner.

③当have在完成时中作为助动词时，其否定形式为have not/has not

肯:They have seen this film.

否：They have not seen this film.

04

一些特殊说明

①肯定陈述句中的some/too，在否定陈述句中应改为any/either。

肯：He has some milk.

否: He hasn’t any milk.

肯：I like Math. Jack like Math, too.

否：I don’t like Math. Jack doesn’t like Math, either.

②肯定陈述句中若有and连接两个并列的成分，在否定陈述句中通常应改为or。

肯：They like bananas and apples.

否：They don't like bananas or apples.

但以下几种状况，不需要改为or

A. 句子中出现两个否定词。

如: Men cannot live without air and water.

B. and列举的成份前都有否定词。

如: It has no eyes and no ears.

C. and列举的成份在否定词前面。

如: Tom and Merry can not write their names.

D. and构成的固定词组。

如: He did not work day and night.

E. and连接两个表示先后发生的动作。

如: Don't drink and drive.