Introduction: what are alternations and how should we study them?

The research paradigm of alternation studies is forming an increasingly large share of the empirical foundations of usage-based linguistics. As the paradigm is essentially an amalgamation of research traditions from various subfields of linguistics, including sociolinguistics, psycholinguistics, cognitive linguistics, and construction grammar, it sports various definitions of the concept of "alternation" and various ways of conducting an alternation study, which are not always compatible. The present special issue is therefore intended to bring researchers from various backgrounds in usage-based linguistics together to see how we can deal with these issues. This introduction first presents the various ways of defining an alternation and discusses the differences between them and how these definitions determine the methodological set-up of an alternation study. Next, the contributions to the special issue are each in turn summarized and related to one another.