It gradually was introduced as a more widespread term to denote that territory, formerly known as Gaul, after the Frankish invasion and the retreat of the Romans.The name "Francia" was applied to various territorial units until the Middle Ages, when it came to signify the kingdom of the French sovereign.The population has more than doubled since the mid-nineteenth century, when it was 28.3 million.The post–World War II period saw fertility increases in the French version of the baby boom, but the birthrate began to drop in the early 1970s. At the turn of the twentieth century and after World War I, migration accounted for half the total population growth. The official language is French, which is by far the majority language, having been imposed on the regional populations since the nineteenth century.The Toubon law of 1994 mandates that French be spoken in all official, public spheres of life.
White is associated with monarchy, red with the republic, and blue with Charlemagne, Clovis, and other early rulers.While most of the country is in a temperate zone, the Mediterranean area is considered to have a subtropical climate.The four main rivers are the Seine, the Loire, the Garonne, and the Rhône. France has a low population density compared to other countries in Western Europe.Regional identities, such as Provencal and Breton have coexisted with political units of state control.The degree to which France is today a homogeneous nation is a highly contested topic.