否定：全部否定和部分否定
eg.All the birds can not fly.
Not all the birds can fly.不是所有的鸟都会飞。
1.部分否定
eg.All the birds can not fly.并非所有的鸟都会飞。
None of the birds can fly.所有的鸟都不会飞。
代词或副词如all，both，every，everybody，every day，everyone，everything，everywhere等与not搭配使用时，表示部分否定，意思为“并非都是"等。
eg.All is not gold that glitters.发光的并非都是金子。= Not all is gold that glitters.
2.全部否定
英语中常用not，none，nobody，nothing，nowhere，neither，never等表示全部否定的概念。
eg.Nothing in the world is difficult for one who sets his mind to it. 世上无难事，只怕有心人。
eg.W:Daddy,I've decided to give up science and go to business school.
M:Well,it is your choice as long as pay your own way,but I should warn you that not everyone with a business degree will make a successful manager.
Q:What do we learn from the conversation?
A.The man doesn't have money for his daughter's graduate studies.
B.The man doesn't think his daughter will get a business degree.
C.The man insists that his daughter should pursue her studies in science.
D.The man advises his daughter to think carefully before making her decision.
双重否定
1.在阅读当中出现的频率更高一些。在一个句子中出现两个否定词：not，never，hardly，scarcely，rarely，seldom，few，little，none等，双重否定表示肯定的概念。
eg.No one can command others who cannot command himself.
A perpson can command others who command himself. 正人先正己。
eg.Without the ability to think critically,to defend their ideas and understand the ideas of others, they can not fully participate in our democracy.
如果没有能力进行批判性思维，维护自己的观点，并理解他人的观点，他们就不能充分的参与我们的民主政治中来。
2.形式否定，意义肯定
eg.A man can never have too many ties. 一个男人可以拥有很多的领带。
A woman can never have too many dresses. 一个女人拥有再多的衣服也不为过。
eg.We can hardly praise his achievement too much. 对他的成就我们无论怎样赞扬也不过分。
eg.A mother can never be patient enough with her child. 一个母亲对她的孩子再怎么耐心也不为过。
A teacher can never be strict enough with his students. 一个老师对他的学生再怎么严格也不为过。
这种形式主要运用于阅读当中。
From:https://www.zgghmh.com/CET-4/20000378.asp