langue d'oc and langue d'oïl, names of the two principal groups of medieval French dialects. Langue d'oc (literally, "language of yes") was spoken south of a line running, roughly, from Bordeaux to Grenoble, whereas langue d'oïl (literally, "language of yes") was prevalent in central and N France. The two dialect groups were named after their respective words for "yes," oc having been the form of "yes" in the south and oïl (now oui) having been used for "yes" in the north. Langue d'oc developed into Occitan, and included Provençcal, a dialect that became the language of the troubadours in the south of France. Of the langue d'oïl dialects, that of the Paris region gradually supplanted all others as the standard idiom and developed into modern French. Both langue d'oïl and langue d'oc dialects persisted, however, in some rural areas as patois, or popular, provincial speech.