The main aim of this book is to apply certain theoretical insights into linguistic variation and change (insights often derived from studies of English and other Germanic languages) to the Spanish-speaking world, a project I first sketched some years ago (Penny 1987). Although I do not claim, on this occasion, to advance variationist theory, it is my hope that the data deployed here will test, and for the most part support, such theoretical approaches to language.

The data used are most frequently Castilian data, but since I am at pains to emphasize that Castilian emerges from a dialect continuum which embraces the whole Peninsula (and indeed extends beyond it), it is inevitable that all varieties of Romance spoken in the Peninsula (therefore including Galician, Portuguese, and Catalan) will at times be the subject of discussion. Similarly, since dialect mixing is a constant theme of the book, it is inevitable that American Spanish (the product of such mixing) will come under close scrutiny.

Two broad themes are pursued. The first is that of the seamlessness of language variation: the fact that language presents itself to us in the form of orderly but undivided heterogeneity. This is to say that variation is almost infinitely subtle, and occurs along all parameters (geographical and social), so that it is usually inappropriate to seek to establish boundaries between varieties, whether we are dealing with geographically ordered varieties, or with socially determined varieties, or with linguistic registers or styles. Each variety merges imperceptibly with those that are adjacent to it, using the term adjacent to refer to varieties which are either socially or geographically contiguous.