This book presents current research on Ulam stability for functional equations and inequalities. Contributions from renowned scientists emphasize fundamental and new results, methods and techniques. Detailed examples are given to theories to further understanding at the graduate level for students in mathematics, physics, and engineering.Key topics covered in this book include:Quasi meansApproximate isometriesFunctional equations in hypergroupsStability of functional equationsFischer-Muszély equationHaar meager sets and Haar null setsDynamical systemsFunctional equations in probability theoryStochastic convex orderingDhombres functional equationNonstandard analysis and Ulam stabilityThis book is dedicated in memory of Staniłsaw Marcin Ulam, who posed the fundamental problem concerning approximate homomorphisms of groups in 1940; which has provided the stimulus for studies in the stability of functional equations and inequalities.