one of two groups of the modern Celtic languages; the group includes Irish (Irish language), Manx (Manx language), and Scottish Gaelic (Scots Gaelic language). The Goidelic languages originated in Ireland and are distinguished from the other group of Insular Celtic tongues—the Brythonic (Brythonic languages)—by the retention of the sound q (later developing to k, spelled c), where Brythonic has developed a p sound. Both sounds are assumed to be derived from an ancestral form *k^w in the Indo-European parent language. (An asterisk identifies a sound as a hypothetical and reconstructed form.) Because of this k (or q) sound, the Goidelic languages are sometimes referred to as Q-Celtic.