There are several well-supported theories about the origin of the Romanians. It is without doubt that the Romanian language is descended from the Vulgar Latin dialects spoken in the Roman provinces north of the "Jireček Line" (a proposed notional line separating the predominantly Latin-speaking territories from the Greek-speaking lands in Southeastern Europe) in Late Antiquity. The theory of Daco-Roman continuity argues that the Romanians are mainly descended from the Daco-Romans, a people developing through the cohabitation of the native Dacians and the Roman colonists in the province of Dacia Traiana (primarily in present-day Romania) north of the river Danube. The competing immigrationist theory states that the Romanians' ethnogenesis commenced in the provinces south of the river with Romanized local populations (known as Vlachs in the Middle Ages) spreading through mountain refuges, both south to Greece and north through the Carpathian Mountains. According to the "admigration theory", migrations from the Balkan Peninsula to the lands north of the Danube contributed to the survival of a Romance-speaking population in those territories.
Romanians, known by the exonym Vlachs in the Middle Ages, speak a language descended from the Vulgar Latin that was once spoken in south-eastern Europe. Inscriptions from the Roman period prove that a line, known as the "Jireček Line", can be drawn through the Balkan Peninsula, which separated the Latin-speaking northern provinces, including Dacia, Moesia and Pannonia from the southern regions where Greek remained the predominant language.Eastern Romance now has four variants, which are former dialects of a Proto-Romanian language.Daco-Romanian, the official language of Romania, is the most widespread of the four variants. Speakers of the Aromanian language live in scattered communities in Albania, Bulgaria, Greece and Macedonia. Another two, by now nearly extinct variants, Megleno-Romanian and Istro-Romanian, are spoken in some villages in Macedonia and Greece, and in Croatia, respectively.