!=

Definition: "not equal to." Background: In most popular programming languages, "!" belongs to a class of operators known as "logic operators." Basically, it just stands for "not", "opposite", or "false", depending on what the context is. Two other operators are in this class: "||" for "or", and "&&" for "and". "!=" belongs to another class of operators called "comparison operators." Also in this class are things like "==" (equals), ">=" (greater than or equal to), "<" (less than), etc.