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Why are Goidelic languages sometimes called Q-Celtic languages?
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Celtic languages
Britannica editor Jeff Wallenfeldt provides an overview of the Irish language.
Goidelic languagesâwhich include Irish, Manx, and Scottish Gaelicâare referred to as Q-Celtic because they retain a k or q sound where other Celtic languages, specifically the Brythonic group, developed a p sound.12
Both of these sounds are derived from the ancestral Indo-European labiovelar sound *kʡ. While the Brythonic languages (sometimes called P-Celtic) shifted this sound to p, the Goidelic languages maintained the velar q (which later developed into the k sound spelled as c).12
It is important to note that while these terms are used to describe these linguistic differences, some scholars argue that using a single sound shift to classify these language groups is not fully justified.3