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Why are Brythonic languages sometimes called P-Celtic languages?
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Celtic languages
Britannica editor Jeff Wallenfeldt provides an overview of the Irish language.
Brythonic languagesâwhich include Welsh, Cornish, and Bretonâare referred to as P-Celtic because they developed a p sound where other Celtic languages, specifically the Goidelic group, retained a k sound (spelled c, and earlier q).12
Both the p and k sounds are derived from the same ancestral form, the Indo-European *kw. While these terms are sometimes used to categorize these languages based on this specific sound shift, some linguists argue that using a single phonological change to classify entire language groups is not fully justified.123