Brythonic is one of two major divisions of modern-day Celtic languages (the other being Goidelic). Also known as P-Celtic, for the way it uses a "P" to begin words that, in the hypothetical base Indo-European language, began with "Qu".
The main living Brythonic languages are Breton and Welsh; other notable tongues are Cornish (which has no native speakers, but is being resurrected), and probably the extinct Pictish (although the late Kenneth H. Jackson argued during the 1950s, from some of the few remaining examples of Pictish that Pictish was a non-Indo-European language, the majority of modern Pictish scholars do not agree). Once, Brythonic languages encompassed most of Great Britain (though not Ireland), but they were driven to the fringes of that island by the invasions of the Angles, Saxons, and Jutes which brought English to Britain. Brythonic languages then disappeared from Scotland after Irish colonists brought a Goidelic language with them from their home island.