Fuzzy logic is a form of various-valued logic; it deals with reasoning that is approximate rather than fixed & exact. In contrast with traditional logic theory, where binary sets have two-valued logic: true or false, fuzzy logic variables may have a truth value that ranges in degree among 0 and 1. Fuzzy logic has been extended to handle the concept of partial truth, where the truth value may range among completely true and completely false. Furthermore, when linguistic variables are used, these degrees may be handled by specific functions.