ABSTRACT
Over the past two decades, there has been a rapid growth in the number and variety of applications in fuzzy sets and theory. In this chapter, the authors present some important concepts, notations, and definitions of fuzzy set theory. Membership function fully defines the fuzzy set which is the major component of fuzzy set theory and it enables the fuzzy approach to access uncertain and ambiguous matters. In most situations, when the universe of discourse X is in continuous space, usually the X is partitioned into several fuzzy subsets. The fuzzy set theoretic operators may not be limited to basic operators. There are many operators which have been suggested by mathematicians over the past four decades.
