Preface; Further information; 1. Axiomatic motivation of vector addition; 2. Cauchy's equation: Hamel basis; 3. Three further Cauchy equations: an application to information theory; 4. Generalizations of Cauchy's equations to several multiplace vector and matrix functions: an application to geometric objects; 5. Cauchy's equations for complex functions: applications to harmonic analysis and to information measures; 6. Conditional Cauchy equations: an application to geometry and a characterization of the Heaviside functions; 7. Addundancy, extensions, quasi-extensions and extensions almost everywhere: applications to harmonic analysis and to rational decision making; 8. D'Alembert's functional equation: an application to noneuclidean mechanics; 9. Images of sets and functional equations: applications to relativity theory and to additive functions bounded on particular sets; 10. Some applications of functional equations in functional analysis, in the geometry of Banach spaces and in valauation theory; 11. Characterizations of inner product spaces: an application to gas dynamics; 12. Some related equations and systems of equations: applications to combinatorics and Markov processes; 13. Equations for trigonometric and similar functions; 14. A class of equations generalizing d'Alembert and Cauchy Pexider-type equations; 15. A further generalization of Pexider's equation: a uniqueness theorem: an application to mean values; 16. More about conditional Cauchy equations: applications to additive number theoretical functions and to coding theory; 17. Mean values, mediality and self-distributivity; 18. Generalized mediality: connection to webs and nomograms; 19. Further composite equations: an application to averaging theory; 20. Homogeneity and some generalizations: applications to economics; 21. Historical notes; Notations and symbols; Hints to selected 'exercises and further results'; Bibliography; Author index; Subject index.