Contributions from both well-known practitioners and new voices in the areas of language typology, historical linguistics, and function-based approaches to language description define this volume, as does its foci in two major geographical areas — southeast Asia and northwestern North America. All of the papers appeal, in one way or another, to functional-historical approaches to explanation. Behind this appeal lies an assumption that languages are selective in their development in ways that are dependent upon the communicative tasks to which they are put. As such, language function accounts for both variation and historical development over time.