Common Brittonic

Common Brittonic (Welsh: Brythoneg; Cornish: Brythonek; Breton: Predeneg), also known as Common Brythonic, British, or Proto-Brittonic, is the reconstructed Celtic language thought to be historically spoken by the Celtic Britons in Britain and Brittany. It is the common ancestor of the later Brittonic languages.

It is a form of Insular Celtic, descended from Proto-Celtic, a theorized parent language that, by the first half of the first millennium BC, was diverging into separate dialects or languages. Evidence from early and modern Welsh shows that Common Brittonic was influenced by Latin during the Roman period, especially in terms related to the church and Christianity. By the sixth century AD, the languages of the Celtic Britons were swiftly diverging into Neo-Brittonic: Welsh, Cumbric, Cornish, Breton. Pictish may either have been one of Brythonic languages or a descendant of a close separate branch.

Over the next three centuries, Brittonic was replaced by Scottish Gaelic in most of Scotland, and by Old English (from which descend Modern English and Scots) throughout most of modern England as well as Scotland south of the Firth of Forth. Cumbric disappeared in the 12th century, and in the far south-west, Cornish probably became extinct in the 18th century, though it has since been revived. Welsh and Breton are the only daughter languages that have survived fully into the modern day.