陈述的否定句和否定回答缩写与否都可以，不过一般在否定回答时多用缩写形式，另外，am和not无论什么情况下是绝对不能缩写的。还有反义疑问句的后半部如果是否定形式是必须缩写的。
否定句的形式有哪些
（1）一般否定句
I don't know this. No news is good news.
There is no person（smoking）/not a person/not any person（smoking）in the house.
（2）特指否定
He went to his office, not to see him.
I am sorry for not coming on time.
I don't think / believe/suppose / feel / imagine you are right.
（3）部分否定
All the answers are not right
All is not gold that glitters
I don't know all of them.
I can't see everybody/everything.
Both of them are not right.
（4）全体否定
None of my friends smoke.
I can see nothing/nobody.
Neither of them is right.
Nothing can be so simple as this.
（5）延续否定
You didn't see him, neither/nor did I.
You don't know, I don't know either.
He doesn't know English, let alone / to say nothing of/not to speak of（更不用说）French.
（6）半否定句
We seldom/hardly/scarcely/barely hear such fine singing.
I know little English. I saw few people.
（7）双重否定
You can't make something out of nothing.
What's done cannot be undone.
There is no sweet without sweat.
No gain without pains.
I can't help /keep/ laughing whenever I hear it.
No man is so old but（that）he can learn.
（8）排除否定
Everyone is ready except you.
He did nothing but play.
But for your help, I couldn't do it.
（9）加强否定
I won't do it at all.