The celtic languages are a group of languages descended from proto-celtic (and a branch of the indo-Europoean language family).
These languages were spoken over a wide area of Europe from Britain and Spain to the Balkans. Not much is known of the celtic of that era. The primary sources for reconstruction (of proto-celtic) come from the literature of Middle Welsh (e.g. the Mabinogion dating back to 1350) and Old Irish (e.g. the Cambrai Homily).
The celtic languages are divided into two groups: Brittonic and Goidelic. Britonnic (or British Celtic languages) are all descended from the root language Common Britonnic spoken in Britain and Brittany.
Breton, Cornish, Cumbric, Welsh
Irish, Scottish Gaelic, Manx