This volume brings together the latest research from leading scholars on the mental lexicon - the representation of language in the mind/brain at the level of individual words and meaningful sub-word units. In recent years, the study of words as mental objects has grown rapidly across several fields, including linguistics, psychology, philosophy, neuroscience, education, and cognitive science. This comprehensive collection spans multiple disciplines, topics, theories, and methods to highlight important advances in the study of the mental lexicon, identify areas of debate, and inspire innovation in the field from present and future generations of scholars. The book is divided into three parts. Part I presents modern linguistic and cognitive theories of how the mind/brain represents words at the phonological, morphological, syntactic, semantic, and pragmatic levels. This part also discusses broad architectural issues pertaining to the internal organization of the lexicon, the relation between words and concepts, and the role of compositionality. Part II examines how children learn the form and meaning of words in their native language, bridging learner- and environment-driven contributions and taking into account variability across both individual learners and communities. Chapters in the final part explore how the mental lexicon contributes to language use during listening, speaking, and conversation, and includes perspectives from bilingualism, sign languages, and disorders of lexical access and production.