An expression that results in a value of either TRUE or FALSE. For example, the expression
2 < 5 (2 is less than 5)
is a Boolean expression because the result is TRUE. All expressions that contain relational operators , such as the less than sign (<), are Boolean. The operators -- AND, OR, XOR, NOR, and NOT -- are Boolean operators.
Boolean expressions are also called comparison expressions, conditional expressions, and relational expressions.