
Negation is an unary operation that changes the truth value of a logical object.^{[1]} If the value is true, negation changes the value to false. If the value is false, negation changes the value to true. The negative of a negative of a proposition, called a double negative, is equal to the original proposition: .^{[2]} This means that a double negative can be eliminated from a proposition without changing the truth value of the proposition. 
There are a number of different ways to write negation. See table 2.
Notation  Pronounced  Description 

'not A'  This notation is used in mathematics. Since it is not found on a standard computer keyboard, one of the other notations are usually substituted for nonprofessional publications.  
'not A'  This notation is used in mathematics.  
'not A'  This notation is used in mathematics. Either ¬A or ~A are preferred.  
'bar A'  This notation is used in mathematics.  
'A prime' or 'A complement'  This notation is often used in set theory.  
'bang A'  This notation is used in most computer languages and some mathematics software.  
'not A'  This notation is used in the computer language fortran.  
Table 2: Negation notation. 
#  A  B  C  D 
E  F  G  H  I 
J  K  L  M  N 
O  P  Q  R  S 
T  U  V  W  X 
Y  Z 
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