Mag: 'a plain' (pronounced moy)
Mag Ai: the great plain in the County Roscommon, extending from Ballymore to Elphin, and from Bellanagare to Strokestown (pronounced Moy wee)
Mag Breg: the plain along and south of the lower Boyne, comprising the east of County Meath and the north of County Dublin (pronounced Moy bray)
Mag Cruimm: south-east of Cruachan, in Connacht
Mag Dea: a plain in Ulster
Mag Dula: a plain though which the Do flows by Castledawson into Lough Neagh
Mag Eola: a plain in Ulster
Mag Inis: the plain comprising the baronies of Lecale and Upper Castlereagh, in the County Down
Mag Linè: Moylinne, a plain to the north-east of Lough Neagh, in the barony of Upper Antrim
Mag Mucceda: a plain near Emain Macha