Category change, broadly defined as the shift from one word class to another, is often studied as part of other changes, such as grammaticalization or lexicalization, but not in its own right. This volume offers a survey of different types of category change and their properties, e.g. abrupt versus gradual changes, morphological versus syntactic changes, or context-independent versus context-sensitive changes. The purpose of this collection of papers is to explore the concepts of linguistic category and category change from the perspective of Construction Grammar. Using data from a variety of languages, the authors address a number of themes that are central to current theorizing about category change, such as the question of whether or not categories should be considered discrete entities, how new categories arise, or whether category change can be considered as the emergence of a new construction, i.e. a new form-meaning pairing. The novel approach advanced in this volume will be of interest to historical linguists as well as to general linguists working on the nature of linguistic categories.