Western Brythonic was one of two dialect

Dialect

The term dialect is used in two distinct ways, even by linguists. One usage refers to a variety of a language that is a characteristic of a particular group of the language's speakers. The term is applied most often to regional speech patterns, but a dialect may also be defined by other factors,...

s into which the British language split during the Early Middle Ages

Early Middle Ages

The Early Middle Ages was the period of European history lasting from the 5th century to approximately 1000. The Early Middle Ages followed the decline of the Western Roman Empire and preceded the High Middle Ages...

; its counterpart was Southwestern Brythonic. The reason and date for the split is often given as the Battle of Deorham

Battle of Deorham

The Battle of Deorham or Dyrham was fought in 577 between the West Saxons under Ceawlin and Cuthwine and the Britons of the West Country. The location, Deorham, is usually taken to refer to Dyrham in South Gloucestershire. The battle was a major victory for the West Saxons, who took three important...

 in 577, at which point the victorious Saxons

Saxons

The Saxons were a confederation of Germanic tribes originating on the North German plain. The Saxons earliest known area of settlement is Northern Albingia, an area approximately that of modern Holstein...

 of Wessex

Wessex

The Kingdom of Wessex or Kingdom of the West Saxons was an Anglo-Saxon kingdom of the West Saxons, in South West England, from the 6th century, until the emergence of a united English state in the 10th century, under the Wessex dynasty. It was to be an earldom after Canute the Great's conquest...

 essentially cut the Brythonic-speaking Britain in two. Western Brythonic was spoken in Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 and the Hen Ogledd

Hen Ogledd

Yr Hen Ogledd is a Welsh term used by scholars to refer to those parts of what is now northern England and southern Scotland in the years between 500 and the Viking invasions of c. 800, with particular interest in the Brythonic-speaking peoples who lived there.The term is derived from heroic...

, or "Old North", the Brythonic-speaking area of northern England

Northern England

Northern England, also known as the North of England, the North or the North Country, is a cultural region of England. It is not an official government region, but rather an informal amalgamation of counties. The southern extent of the region is roughly the River Trent, while the North is bordered...

 and southern Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

. It became the ancestor to Old Welsh and the extinct dialect or language known as Cumbric

Cumbric language

Cumbric was a variety of the Celtic British language spoken during the Early Middle Ages in the Hen Ogledd or "Old North", or what is now northern England and southern Lowland Scotland, the area anciently known as Cumbria. It was closely related to Old Welsh and the other Brythonic languages...

, and thus to the modern Welsh language

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

. Southwestern Brythonic became the ancestor to Cornish

Cornish language

Cornish is a Brythonic Celtic language and a recognised minority language of the United Kingdom. Along with Welsh and Breton, it is directly descended from the ancient British language spoken throughout much of Britain before the English language came to dominate...

 and Breton

Breton language

Breton is a Celtic language spoken in Brittany , France. Breton is a Brythonic language, descended from the Celtic British language brought from Great Britain to Armorica by migrating Britons during the Early Middle Ages. Like the other Brythonic languages, Welsh and Cornish, it is classified as...

.