affix back vowel breton language celtiberian language celtic languages central vowel close-mid vowel close vowel continental celtic languages cornish language cumbric language english language front vowel galatian language gaulish language grammar great britain insular celtic languages ireland irish traveller irish diaspora irish language kuno meyer language language death language family latin alphabet lepontic language manx language metathesis mid vowel mixed language near-close vowel near-open vowel noric language open-mid vowel open vowel pictish language romani language scottish gaelic slang syntax unicode verlan vocabulary welsh language writing system