A system which mathematically models complex relationships which are usually handled in a vague manner by language. Under the title of "Fuzzy Logic" falls formal fuzzy logic (a multi-valued form of logic), and fuzzy sets. Fuzzy sets measure the similarity between an object and a group of objects. A member of a fuzzy set can belong to both the set, and its complement. Fuzzy sets can more closely approximate human reasoning than traditional "crisp" sets. See: Crisp sets.