Negation is the process of reversing the meaning of a Boolean expression. There are two approaches used to negate a Boolean expression.

First Approach

The first approach is the easiest one. Just use a NOT operator in front of the original Boolean expression and your negated Boolean expression is ready! For example,

## PHP

if the original Boolean expression is `\$x > 5 && \$y == 3`,

the negated Boolean expression becomes `!(\$x > 5 && \$y == 3)`.

Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as `!\$x > 5 && \$y == 3`. In this case the NOT operator would negate only the first Boolean expression, `\$x > 5`.

## Java, C++, C#

if the original Boolean expression is `x > 5 && y == 3`,

the negated Boolean expression becomes `!(x > 5 && y == 3)`.

Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as `!x > 5 && y == 3`. In this case the NOT operator would negate only the first Boolean expression, `x > 5`.

## Visual Basic

if the original Boolean expression is `x > 5 And y = 3`,

the negated Boolean expression becomes Not `(x > 5 And y = 3)`.

Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as Not `x > 5 And y = 3`. In this case the NOT operator would negate only the first Boolean expression, `x > 5`.

## Python

if the original Boolean expression is `x > 5 and y == 3`,

the negated Boolean expression becomes not `(x > 5 and y == 3)`.

Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as not `x > 5 and y == 3`. In this case the NOT operator would negate only the first Boolean expression, `x > 5`.

Second Approach

The second approach is a little bit more complex but not difficult to learn. All you must do is negate every operator according to the following table.

## PHP

 Original Operator Negated Operator == != != == > <= < >= <= > >= < && || || && ! !

Notice: Please note that the NOT operator ( ! ) remains intact.

For example,

if the original Boolean expression is `\$x > 5 && \$y == 3`,

the negated Boolean expression becomes `\$x <= 5 || \$y != 3`.

## Java, C++, C#

 Original Operator Negated Operator == != != == > <= < >= <= > >= < && || || && ! !

Notice: Please note that the NOT operator ( ! ) remains intact.

For example,

if the original Boolean expression is `x > 5 && y == 3`,

the negated Boolean expression becomes `x <= 5 || y != 3`.

## Visual Basic

 Original Operator Negated Operator = <> <> = > <= < >= <= > >= < And Or Or And Not Not

Notice: Please note that the `Not` operator remains intact.

For example,

if the original Boolean expression is `x > 5 And y = 3`,

the negated Boolean expression becomes `x <= 5 And y <> 3`.

## Python

 Original Operator Negated Operator == != != == > <= < >= <= > >= < in not in not in in and or or and not not

Notice: Please note that the `not` operator remains intact.

For example,

if the original Boolean expression is `x > 5 and y == 3`,

the negated Boolean expression becomes `x <= 5 or y != 3`.