The dagger function can be regarded as stronger variation of the stroke function. When a compound proposition is expressed in terms of stroke function, the rule is that at least one of the components must be false if the stroke function must be true, though the possibility of both being false to make stroke function true is allowed. However, in dagger function, both the components must be false to make it true. This statement is regarded as the definition of dagger function. Suppose p and q are statements forms, then, p NOR q is true if and only if both p and q are false. Otherwise, it is false.