[The first eight chapters of this book concern synchronic patterns of variation in the speech community, with the linguistic variable as the working tool of analysis. There have been hints about linguistic change in progress but it is not until this chapter that sociolinguistics takes on the study of change and variation as its central problem. The concept of apparent time, and its relations in real time, had been explored in the Martha's Vineyard study, but here it is analyzed and explored in much greater detail.

We now have much more information than we had at that time on the extent to which adults change their language as they grow older. It is important to note that from the outset, there was no assumption that they did not: the task is “to distinguish the effects of linguistic change from the invariant effects of aging and from the modifying effects of the present situation upon older speakers.”]

The study of small differences in language behavior is concentrated upon the variable elements in linguistic structure; this procedure brings us inevitably to indications of linguistic change. Variability itself is change: but some types of variation are themselves invariant from generation to generation.We are particularly interested in gradual alterations of the linguistic habits of a population through the course of time, which will be referred to here as linguistic change. The explanation of linguistic change on a large scale is one of the primary goals of linguistics, and in the present work we hope to contribute to that end by the close examination of linguistic change in progress.