Soltanifar, M.Sharafi, H.Hosseinzadeh Lotfi, F.Pedrycz, W.Allahviranloo, T.2024-05-192024-05-1920232198-4182https://doi.org/10.1007/978-3-031-30403-3_3https://hdl.handle.net/20.500.12713/4456In real world, we sometimes face situations where we don’t know which decision is right or wrong, and the correct action is hidden from view. At this time, “fuzzy logic” offers a flexible and valuable proposition. In this way, the amount of uncertainty can be determined for each situation. For this reason, fuzzy logic is sometimes called doubtful logic because its results are created with doubts. In this chapter, this logic begins with the presentation of fuzzy sets and continues with the definitions of fuzzy numbers. Finally, one of the applications of fuzzy numbers, i.e. converting linguistic terms into fuzzy numbers for decision making in fuzzy logic, is presented. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.eninfo:eu-repo/semantics/closedAccessBook Chapter47131452-s2.0-8515994359210.1007/978-3-031-30403-3_3Q4