小学课本范围内的英语其实并不难，掌握好词汇和基础的句型语法，就能游刃有余。
其中，句型之间的相互转换是重点之一。
常见的句型转换有：
①肯定句 改 否定句；
②陈述句 改 一般疑问句；
③陈述句 改 特殊疑问句；
④陈述句 改 感叹句；
⑤陈述句 改 祈使句。
今天我们先给大家讲解系统的讲解下各种句型肯定句变否定句的规则。
肯定句改否定句可大致分为三类：
1.有be动词或者情态动词的肯定句变否定句
2.没有be动词也没有情态动词，有实意动词(表示动作的动词)的肯定句变否定句
3.含有动词have/has的肯定句变否定句
以下对上述三种肯定句变否定句的变化规则依次讲解
有be动词或者情态动词的肯定句变否定句
转变方法：在be动词或情态动词后面直接加not
例1. I am a student. → I am not a student.
例2. You are sad. → You are not sad.
例3. I can swim. → I can not swim.
例4. You will go to the park.
→ You will not go to the park.
没有be动词也没有情态动词，有实意动词(表示动作的动词)的肯定句变否定句
转变方法：借助助动词（do, does, did）来帮助否定
①当句中的动词是原形时，加don't。
例1.I like English.
→ I do not like English.
例2.You have dinner.
→ You 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。
例1. She likes singing.
→She doesn't like singing.
例2. She does her homework.
→ She does not do her homework.
③当句中的动词是过去式时，用didn't，加动词原形
例: We had a great time during our holidays.
→We did not have a great time during our holidays.
动词have/has的特殊说明:
①当have表示“某人有什么的时候”，其否定形式为have not/has not
例: She has two books.
→ She has 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
例: You have dinner.
→You do 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
例: I have seen this film.
→ I have not seen this film.
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。
例1.He has some milk.
→ He hasn’t any milk.
例2. I have books. She has books,too.
→ I have not books. She has not books,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。
例: There are students and teachers in the classroom.
→There are not students or teachers in the classroom.
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.
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