This book discusses the nature and definition of what a word is in Linguistics. This is not an easy task since the term subsumes a wide range of phenomena explored from an even wider array of perspectives. Although words are the most accessible linguistic units from the speaker’s introspection viewpoint, they are, at the same time, an incredibly elusive reality for the linguist. Issues such as their definition, theoretical status, limits, characteristics, and psycholinguistic reality are still controversial and open for debate.This book offers an up-to-date overview of the latest discussions on the nature of word in Modern Linguistics. It gathers together under a single collective volume different views of what a word is from a wide range of diverse methodological and theoretical linguistic frameworks, such as phonological theory, linguistic typology, lexical generative morphology, generative syntax, cognitive grammar, and construction grammar. Despite their different backgrounds, all these papers are geared towards the same goal: to offer a detailed account of what a word is in their respective fields.All in all, this collection of papers offers different perspectives that will contribute to provide some answers to the myriad of questions that a simple phrase such as to be or not to be a Word brings to the fore.