Introduction to Negation and the NOT Operator

In the previous post, we have learned the difference between and and or. And and or are called logical operators. Statements that are connected by logical operators are called logical expressions.

In this post, we are going to learn another logical operator which is a logical operator for negation.

The negation of a given statement p is called not p, that if true, exactly expresses what it would mean to be false. 

The truth table of the NOT operator is shown below. As we can see, a true statement when negated is true, and a false statement when negated is true.

not operator

Note that the negation of a statement is simply putting the not operator in front of it and not finding the opposite word for it. For example, the negation of beautiful is not beautiful; we cannot negate beautiful with ugly. 

not operator 2

If two logical expressions have the same truth values, then, they are said to be logically equivalent.  For example, the expression p and not (not p) are logically equivalent as shown in the previous truth table.