popular Latin (Latin sermo vulgaris, colloquial speech), traditional term used to designate the living language of the masses of the people in the Roman Empire (beginning in the third to second century B.C.). Cicero, Quintillian, and others made the distinction between Vulgar Latin and literary Latin (sermo latina and lingua latino). During the fall of the Roman Empire in the.fourth and fifth centuries the single Latin language gradually underwent a process of differentiation. As a result of political and social changes the living Latin speech began to penetrate all areas of life. Because of the absence of political and cultural contact, the so-called popular Latin developed in different ways in various parts of the former Roman Empire, thus leading to the formation of the independent Romance languages in the ninth century.