一.概念

   否定句指否定陈述句的句子.

二.相关知识点精讲  

1.    用not构成的否定句：主语+助动词/ be+not+…

例句：

He is not back yet.

It is not true.

We haven’t forgotten you.

You shouldn’t be so silly.

We haven’t been invited yet.

He won’t go, but they will.

Money could not buy happiness.

I like the salad, but I don’t like this soup.

He wants a girl friend, but he doesn’t want to get married.

You didn’t understand what I said, did you ?

You needn’t try to explain.

I didn’t use to like opera, but now I’m getting interested.

I usedn’t to like opera, but now I’m getting interested.

2.    祈使句的否定句：Don’t+动词原形…。

例句：

Don’t worry. I’ll look after you.

Don’t believe a word he says.

Don’t be so rude.

3. 非谓语动词（不定式，分词，动名词）的否定式：把not放在to do; doing; 的前面。

It’s important not to worry.

He said he deeply regretted not being able to help.

Not knowing what to do, Shelly asked advice of her friend.

He reproached me for not having told it to him.

4. not与除谓语以外的其他句子成分连用：

Come early, but not before six.

It’s working, but not properly.

I believe he will succeed, though not without some difficulty.

not用在I hope; I believe; I’m afraid; I guess; I suppose; I expect之后，构成省略句。

—Will it snow today ?

—I hope not.

5. 用no构成否定句：no+名词（单，复数，不可数）相当于not+ a +名词/ not + any +名词

No machine would work for long if it were not properly lubricated.

The nations of Europe and America have found that no country can produce all its needs without trading.

Take that towel, I have no other.