Reactive systems are becoming more and more important for essentially all areas of technical and professional activities as well as for many areas of everyday life. The design of these systems is a great challenge and requires sound compromises between safety and time-to-market. To meet these needs, early design phases nowadays include verification of given specifications against system descriptions to find potential design errors as early as possible. This book is devoted to the foundation of the most popular formal methods for the specification and verification of reactive systems. In particular, the -calculus, omega-automata, and temporal logics are covered in full detail; their relationship and state-of-the-art verification procedures based on these formal approaches are presented. Furthermore, the advantages and disadvantages of the formalisms from particular points of view are analyzed. Most results are given with detailed proofs, so that the presentation is almost self-contained. This book is targeted to advanced students, lecturers and researchers in the area of formal methods.