An Informal Introduction to Language Equations.- Basic Definitions.- Classical Language Equations and the Substitution Property.- Boolean Language Equations.- More on Generalized Derivatives.- Star Equations.- Explicit Equations Over a One-Letter Alphabet.- Implicit Equations With Union and Left Concatenation.- Implicit Equations Over äaü With Union, Concatenation and Star.- Explicit Relations With Union and Left-Concatenation.- Implicit Relations With Union and Left-Concatenation.- Two-Sided Language Equations.- Mixed Systems.- Open Problems.

Beginning with an informal introduction to language equations, this book presents a framework for a general theory for solving systems of equations and relations between languages. Classical language equations, generalized derivatives, Boolean language equations, and implicit equations are presented systematically. An exploration of mixed systems and open problems rounds out the presentation.