Language may not determine the way we think, but it does influence the way we perceive and remember, and it affects the ease with which we perform me… - David Crystal

The main metaphor that is used to explain the historical relationship is that of the language family or family tree.

We now know that linguistic change does not operate in such an across-the-board manner. Some speakers introduce the change into their speech before others; some use it more frequently and consistently than others; and some words are affected before others. A more accurate view is to think of a change gradually spreading through the words of a language – a view that is known as a lexical diffusion. At first just a few people use a change sporadically in a few words (commonly occurring words are influenced very quickly); then a large number of words are affected, with the sound gradually being used more consistently; then the majority of the words take up the change.

The growth in linguistic awareness about the problem, and the emergence of an associated activism, was one of the most exciting developments of the 1990s. Although awareness is still poor among the general public, the issues are now being much more widely discussed at professional levels, in a variety of international, national, regional, and local contexts. At one extreme, there are major campaigns such as those involved in promulgating the Barcelona Declaration of Linguistic Rights, or such initiatives as the `Red Book on Endangered Languages’ (part of the Tokyo Clearing House project). At the other extreme, there is lively debate taking place within many of the endangered communities themselves. Mechanisms and structures are now in place to channel energies.