ad.

1. 不
   He is not a member of the Union.

   他不是工會會員。

2. （用來代替並否定一個詞組或句子）不，不會
   Drop that gun! If not, you'll be sorry.

   把槍扔下！否則你會後悔的。

3. （與否定詞一起構成雙重否定表肯定）並非，不怎麼
   They refused her request not without good reason.

   他們不無道理地拒絕了她的請求。

4. （與all, both, every連用表示部分否定）不都是，不全是
   Both houses are not white.

   兩所房子不都是白色的。

adv.

1. (also n't joined to a preceding verb) used chiefly with an auxiliary verb or ‘be’ to form the negative.
2. used as a short substitute for a negative clause.
3. used to express the negative of other words.
   ▸used with a quantifier to exclude a person or part of a group.
   ▸less than.
4. used in understatements to suggest that the opposite of a following word or phrase is true:
   not a million miles away.
   ▸informal, humorous following and emphatically negating a statement:

   that sounds like quality entertainment—not!

n.

1. a logical operation which gives the value zero if the operand is one, and vice versa.
2. [as modifier] Electronics  denoting a gate circuit which produces an output only when there is no input signal.