This book is an accessible introduction to learnability theory and its interactions with linguistic theories. Working within the principles and parameters framework, the book surveys general concepts from formal learning theory and complexity theory, together with important findings from developmental psycholinguistics, historical linguistics, and language processing. The book examines techniques that can be used to obtain interesting and empirically testable predictions from parametric theories of language variation and includes chapters on syntax, diachronic syntax, and the relationship between linguistic complexity and the form of parameters. Exercises to test readers on their understanding are also included. The book is divided into five chapters: "A Brief Overview of Learnability" (Stefano Bertolo); "Learnability and the Acquisition of Syntax" (Martin Atkinson); "Language Change and Learnability" (Ian Roberts); "Information Theory, Complexity, and Linguistic Descriptions" (Robin Clark); and "The Structural Triggers Learner" (William G. Sakas, Janet D. Fodor). A subject index is also included. (Contains 197 references.) (KFT)