The langues d'oïl are a dialect continuum that includes standard French and its closest relatives historically spoken in the northern half of France, southern Belgium, and the Channel Islands. They belong to the larger category of Gallo-Romance languages, which also include the historical languages of east-central France and western Switzerland, southern France, portions of northern Italy, the Val d'Aran in Spain, and under certain acceptations those of Catalonia.
Linguists divide the Romance languages of France, and especially of Medieval France, into two main geographical subgroups: the langues d'oïl to the North, and the langues d'oc in the Southern half of France. Both groups are named after the word for "yes" in their recent ancestral languages. The most common modern langue d'oïl is standard French, in which the ancestral "oïl" has become oui.