"Fuzzy Logic in Its 50th Year" offers a comprehensive analysis of fuzzy set theory and its developments over a span of five decades. The book discusses various types of fuzzy sets, including ordinary and hesitant fuzzy sets, and is explained by the developers of these concepts, who are recognized as leading scientists in the field. It highlights current theorems and proofs and demonstrates how fuzzy set theory is applied in nearly all areas of science, including health sciences, decision sciences, earth sciences, and social sciences. Additionally, numerous practical applications are presented, ranging from routing problems to robotics and from agriculture to engineering. This book serves as a valuable reference for researchers, educators, and graduate students engaged with new extensions of fuzzy set theory.