sentences:  The end of the early Middle Ages was the time that the Welsh language transitioned from the Primitive Welsh spoken throughout the era into Old Welsh, and the time when the modern England–Wales border would take its near-final form, a line broadly followed by Offa's Dyke, a late eighth-century earthwork.Successful unification into something recognisable as a Welsh state would come in the next era under the descendants of Merfyn Frych.Wales was rural throughout the era, characterised by small settlements called "trefi".