Brittany has also been referred to as Less, Lesser or Little Britain (as opposed to Great Britain, with which it shares an etymology). It is bordered by the English Channel to the north, the Celtic Sea and the Atlantic Ocean to the west, and the Bay of Biscay to the south. Its land area is 34,023 km² (13,136 sq mi).
Brittany is the site of some of the world's oldest standing architecture, home to the Barnenez, the Tumulus Saint-Michel and others, which date to the early 5th millennium BC. Today, the historical province of Brittany is now split among five French departments: Finistère in the west, Côtes-d'Armor in the north, Ille-et-Vilaine in the north east, Loire-Atlantique in the south east and Morbihan in the south on the Bay of Biscay. Since reorganisation in 1956, the modern administrative region of Brittany comprises only four of the five Breton departments, or 80% of historical Brittany. The remaining area of old Brittany, the Loire-Atlantique department around Nantes, now forms part of the Pays de la Loire region.
At the 2010 census, the population of historic Brittany was estimated to be 4,475,295. Of these, 71% lived in the region of Brittany, while 29% lived in the Loire-Atlantique department. In 2012, the largest metropolitan areas were Nantes (897,713 inhabitants), Rennes (690,467 inhabitants), and Brest (314,844 inhabitants). Brittany is the traditional homeland of the Breton people and is recognised by the Celtic League as one of the six Celtic nations, retaining a distinct cultural identity that reflects its history. A nationalist movement seeks greater autonomy within the French Republic.
The word Brittany, along with its French, Breton and Gallo equivalents Bretagne, Breizh and Bertaèyn, derive from the Latin Britannia, which means "Britons' land". This word had been used by the Romans since the 1st century to refer to Great Britain, and more specifically the Roman province of Britain. This word derives from a Greek word, Πρεττανικη (Prettanike) or Βρεττανίαι (Brettaniai), used by Pytheas, an explorer from Massalia who visited the British Islands around 320 BC. The Greek word itself comes from the common Brythonic ethnonym reconstructed as *Pritani, itself from Proto-Celtic '*Kʷritanī from Proto-Indo-European *kʷer ' to do. The Romans called Brittany Armorica, together with a quite indefinite region that extended along the English Channel coast from the Seine estuary to the Loire estuary, and according to several sources, maybe along the Atlantic coast to the Garonne estuary. This term probably comes from a Gallic word, aremorica, which means "close to the sea". Another name, Letauia (in English "Litavis"), was used until the 12th century. It possibly means "wide and flat" or "to expand" and it gave the Welsh name for Brittany: Llydaw.
After the fall of the Western Roman Empire, many Britons settled in western Armorica, and the region started to be called Britannia, although this name only replaced Armorica in the sixth century or perhaps by the end of the fifth. Later, authors like Geoffrey of Monmouth used the terms Britannia minor and Britannia major to distinguish Brittany from Britain.