Negation

In boolean algebra, logical negation is a unary logical operator that reverses the truth value of its operand. The negation of the statement p is written in various ways:

~p,   ¬p,   p,   NOT p   or   !p

It is read as "not p". For instance, if p denotes the statement "today is Saturday", then its negation ~p is the statement "today is not Saturday".

In classical logic, double negation means affirmation, i.e. the statements p and ~(~p) are logically equivalent.