5. Change and spread

The main explanation for regional differences, however, is that, like all other languages in the world, English is constantly changing, and different changes take place in different places. A change may start in a particular location and spread out from there to cover neighbouring areas. Some of these changes may spread so much that they eventually cover the whole country. More often, though, changes will only spread so far, leading to dialect differences between areas which have the new form and areas which do not. The fact that Western traditional dialects pronounce the r in cart 'carrt' while in the Eastern area people say 'caht', without the r, can be explained in this way. Originally all dialects pronounced the r, but then in the 18th century London English started dropping the r, and for reasons we don't understand this innovation spread eastwards and northwards, but not westwards.

Often the spread of changes will be halted by barriers to communication such as natural barriers which impede communication. One of the most important dialect boundaries in England runs through the Fens, which until quite recently was an isolated, swampy area which was very difficult to get across. People in Norfolk say 'lahf' (laugh) and 'butter' while people in Lincolnshire say 'laff' and 'bootter'. The Norfolk pronunciations are newer, southern forms which are the result of changes which never made it across the Fens into Lincolnshire because very few people made it across, as a result of the difficulties caused by the terrain. The major dialect division in Welsh, too, is between North Wales and South Wales, which are separated from one another by mountainous terrain.

We can also observe the role of political boundaries in weakening communication patterns and thus strengthening dialect differences. If the chief dialect division in Britain today lies on the border between England and Scotland, this is a reflection of the political and administrative divisions between the two countries.