在做练习时，有些题目会要求我们将肯定句变为否定句，这类题型要求同学们能够熟练掌握两种句型之间的转换。并不是所有的否定句都能由肯定句加上否定词构成，在进行转换时也有一些细节问题值得注意，下面跟随小编一起来看一下吧。

首先我们要将陈述句按其所包含的谓语部分分成三类：谓语是be动词的肯定句、谓语是实义动词的肯定句与谓语是情态动词的肯定句。

谓语是be动词的肯定句转换为否定句

直接在be动词后加not。如：is not，are not，am not，was not，were not。

He is a math teacher. → He is not a math teacher.

They were players of the school team. → They were not players of the school team.

谓语是实义动词的肯定句转换为否定句

在动词前加助动词否定形式don’t/doesn’t/didn’t，动词的第三人称单数形式或过去式都转变为动词原形。

He wants to go out. → He doesn’t want to go out.

We had a picnic in the park yesterday. → We didn’t have a picnic in the park yesterday.

谓语是情态动词的肯定句转换为否定句

直接在情态动词后加not。

He can remember the content in detail. → He can not remember the content in detail.

There will be a new building next year. →  There will not be a new building next year.   (will not可以缩写为won’t)

大多数情况下，肯定句转换为否定句只要直接加一个not就可以，但这种情况并不绝对。还有一些需要注意的点，肯定句中的some在否定句中要换成any，在be动词和多数情态动词之后的not可以缩写成n’t，不过也有例外，如won’t。