The Celtic languages of the British Isles can be divided into two groups:
- BRYTHONIC: spoken in Britain, and represented today by Welsh and Cornish.
- GOIDELIC: spoken in Ireland and, eventually, Scotland and the Isle of Man. Irish Gaelic, Scots Gaelic and Manx belong to this group.
Goidelic languages are also categorised as Q-Celtic, whilst Brythonic are P-Celtic. This arises from a major difference between the groups – the substitution of a ‘p’ sound for a ‘q’ sound (i.e. a ‘hard-c’ or ‘k’ sound). For instance, the word ‘head’ is ceann in Gaelic, kione in Manx, but pen in Welsh and Cornish.
Of course, in ancient times the inhabitants of the British Isles did not know they were speaking ‘Celtic’. The languages only became so-described at the beginning of the 18th century. Welsh scholar Edward Lhuyd published his Archæologia Britannica in 1707. Lhuyd had recognized that the Welsh and Cornish languages, and Breton, were related to Gaelic. He produced a ‘Comparative Vocabulary’, in which Latin words were given their equivalents in Welsh, Cornish, Breton and Irish. This he referred to as: “a sort of Latin-Celtic Dictionary”.