This book offers a comprehensive review of the different types of fuzzy sets that have been developed in the last few years. Each chapter is dedicated to a type of fuzzy set, which is at first introduced and described in detail, together with its properties. In turn, its application in an optimization and/or decision-making problem is discussed. In particular, the book highlights current research gaps and future research directions on fuzzy numbers in decision analysis and transportation problems. It is intended as a self-contained reference guide for scientists and engineers interested in applying fuzzy set theory for solving optimization problems.