None of these changes happened overnight. They were gradual and probably difficult to discern while they were in progress. Although some changes can be linked to major social changes caused by wars, invasions and other upheavals, the most pervasive source of change in language seems to be in the continual process of cultural transmission. Each new generation has to find a way of using the language of the previous generation. In this unending process whereby each individual child has to “recreate” the language of the community, there is an unavoidable propensity to pick up some elements exactly and others only approximately. There is also the occasional desire to be different. Given this tenuous transmission process, it should be expected that languages will not remain stable and that change and variation are inevitable.

In this chapter, we have concentrated on variation in language viewed diachronically, that is, from the historical perspective of change through time. The type of variation that can be viewed synchronically, that is, in terms of differences within one language in different places and among different groups at the same time, is the subject of the next two chapters.