Features are a central concept in linguistic analysis. They are the basic building blocks of linguistic units, such as words. For many linguists they offer the most revealing way to explore the nature of language. Familiar features are Number (singular, plural, dual, ), Person (1st, 2nd, 3rd) and Tense (present, past, ...). Features have a major role in contemporary linguistics, from the most abstract theorizing to the most applied computational applications, yet little is firmly established about their status. They are used, but are little discussed and poorly understood. In this unique...