 Word meaning has played a somewhat marginal role in early contemporary philosophy of language, which was primarily concerned with the structural features of sentence meaning and showed less interest in the nature of the word-level input to compositional processes. Nowadays, it is well-established that the study of word meaning is crucial to the inquiry into the fundamental properties of human language. This entry provides an overview of the way issues related to word meaning have been explored in analytic philosophy and a summary of relevant research on the subject in neighboring scientific domains. Though the main focus will be on philosophical problems, contributions from linguistics, psychology, neuroscience and artificial intelligence will also be considered, since research on word meaning is highly interdisciplinary.