The 'Discriminative Lexicon Model' is a new theory of how we process words, which moves radically away from most standard theories of morphology. This book introduces the Discriminative Lexicon from both a practical and a theoretical perspective. The first half explains the basic theory and the main parts of 'JudiLing', the Julia package implementing the theory. This is complimented by theory boxes introducing the core concepts underlying the model, such as Matrix Multiplication and the Rescorla-Wagner learning rule. The second half provides a series of case studies spanning languages as diverse as Maltese, Biblical Hebrew, Dutch, Navajo, Estonian and French, as well as multilingual settings. It also shows how behavioural data like lexical decision reaction times, acoustic durations or tongue movements can be modelled. These are accompanied by practice exercises. It is essential reading for researchers and students in a wide range of linguistic fields, including phonetics and computational linguistics.