The Breton language belongs to the Brythonic subdivision of the Celtic group of the Indo-European language family. It is spoken in Brittany, a peninsula in the west of present-day France, where it was brought by settlers from Britain in the fifth century ad. Historically, it has been spoken in Lower Brittany (French Basse-Bretagne; Breton Breizh-Isel), i.e. in the western part of the historic Duchy of Brittany. Today, native speakers are mostly spread throughout rural Brittany, and the language is severely endangered.1

Dialectal divisions

Traditionally, Breton is divided into four major dialect groups, on the basis of the old diocesan borders. These are as follows:

It is often claimed in the literature that the first three dialects are relatively homogeneous, and they are sometimes referred to together as a single dialect grouping called KLT, which is opposed to the Vannetais dialect. The basis for this division is partly philological and partly sociolinguistic. Philologically, Vannetais presents striking differences with respect to the other dialects. Most prominently, it has final stress where other Brythonic varieties show penultimate stress (although it is not universally agreed whether this is a shared innovation or a retention); on the other hand, Vannetais dialects show the sound change of proto- Brythonic *θ to [h]. From a sociolinguistic perspective, Vannetais has had a literary tradition separate from the other Breton dialects (Guillevic and Le Goff 1902).