Focusing on the phonologies of children with functional (non-organic) speech disorders, this volume reports the latest findings in optimality theory, phonological acquisition and disorders. The book is based on typological, cross-sectional, longitudinal, and experimental evidence from over 200 children. It stands out because of the unique test case that the population offers to optimality theory, particularly with respect to puzzles of opacity, lawful orders of acquisition, and language learnability. Beyond its theoretical significance, this research holds clinical relevance for the assessment and treatment of disordered populations, most notably the systematic prediction of learning outcomes. This volume bridges the gap between theory and application by showing how each informs the other. It is intended for linguists, psychologists, speech pathologists, second-language instructors and those interested in the latest developments in phonological theory and its applied extensions.