Breton was brought from Great Britain to Armorica by migrating Britons during the Early Middle Ages; it is thus an Insular Celtic language, and as such not closely related to the Continental Celtic Gaulish language which had been spoken in pre-Roman Gaul. Breton is most closely related to Cornish, both being Southwestern Brittonic languages. Welsh and the extinct Cumbric are the more distantly related Brittonic languages.
The other regional language of Brittany, Gallo, is a langue d'oïl. Gallo is consequently close to French, although not mutually intelligible, and a Romance language descended from Latin (unlike the similarly named ancient Celtic language Gaulish).
Having declined from more than 1 million speakers around 1950 to about 200,000 in the first decade of the 21st century, Breton is classified as "severely endangered" by the UNESCO Atlas of the World's Languages in Danger. However, the number of children attending bilingual classes has risen 33% between 2006 and 2012 to 14,709.
Breton is spoken in Lower Brittany (Breton: Breizh-Izel), roughly to the west of a line linking Plouha (west of Saint-Brieuc) and La Roche-Bernard (east of Vannes). It comes from a Brittonic language community that once extended from Great Britain to Armorica (present-day Brittany) and had even established a toehold in Galicia (in present-day Spain). Old Breton is attested from the 9th century. It was the language of the upper classes until the 12th century, after which it became the language of commoners in Lower Brittany. The nobility, followed by the bourgeoisie, adopted French. The written language of the Duchy of Brittany was Latin, switching to French in the 15th century. There exists a limited tradition of Breton literature. Some Old Breton vocabulary remains in the present day as philosophical and scientific terms in Modern Breton. The recognized stages of the Breton language are: Old Breton - c.800 to c.1100, Middle Breton - c.1100 to c.1650, Modern Breton - c.1650 to present.