A Gaelic kingdom that encompassed Argyll (“Coast of the Gaels”), and the Inner Hebrides of Scotland, along with the area of North-East Ireland that is the modern day County Antrim.
Latin sources referred to the inhabitants of Dalriada as Scoti (Scots or Gaels). It is the Scoti that introduced Christianity to the Britons, along with a new language, Old Irish (sometimes called Old Gaelic).
Old Irish has given rise to the modern day languages of Irish (Gaeilge), Manx (Gaelg or Gailck), and Scottish Gaelic (Gàidhlig).
Each of the four Irish Provinces (Connacht, Leinster, Munster, and Ulster) would each of had their own dialect, with the Dalriada dialect of Scottish-Gaelic being spoken in Antrim.