Vulgar Latin (in Latin, sermo vulgaris, "common speech") is a blanket term covering the vernacular dialects of the Latin language spoken mostly in the western provinces of the Roman Empire until those dialects, diverging still further, evolved into the early Romance languages — a distinction usually made around the ninth century.
This spoken Latin differed from the literary language of classical Latin in its pronunciation, vocabulary, and grammar. Some features of Vulgar Latin did not appear until the late Empire. Other features are likely to have been in place in spoken Latin, in at least its basilectal forms, much earlier. Most definitions of "vulgar Latin" mean that it is a spoken language, rather than a written language, because the evidence suggests that spoken Latin broke up into divergent dialects during this period. Because no one transcribed phonetically the daily speech of any Latin speakers during the period in question, students of Vulgar Latin must study it through indirect methods.