The main aim of this book is to use data from historical spoken corpora as a focal point for the discussion of two related issues: (1) continuity (and change) in spoken grammar, and (2) the factors which appear to sustain certain vernacular grammatical forms for centuries. As the term ‘vernacular’ is central to this study, it is worth defining the sense in which it is used in this book at the outset. The definition of ‘vernacular’ provided by Biber et al. (1999: 1121; my italics) best captures the focus and tenor of this book:

The term vernacular, referring to the popular, untaught variety of a language found in colloquial speech, will serve to cover a range of phenomena in popular speech which may to a greater or lesser extent be felt to lack prestige and to be inappropriate for serious public communication, especially written communication.