Despite the extensive application of fuzzy set theory in modeling real life cases and problems, it has some weaknesses in representing all aspects of the uncertain events of real-world problems. The classical fuzzy logics have two main shortages such as (1) for each property of a system a certain membership function should be defined, and (2) for the choices that there is not enough information available or the choices with equal agree and disagree opinions the classical fuzzy set theory cannot be useful. Therefore, the classical fuzzy set theory is not useful for cases with missing or unrelated data and cases with complex membership functions.