Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, Asia to the east, and the Mediterranean Sea to the south. It comprises the westernmost part of Eurasia. It is the 6th largest continent in the world. Europe is commonly considered to be separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways of the Turkish Straits. Although the term “continent” implies physical geography, the land border is somewhat arbitrary and has been redefined several times since its first conception in classical antiquity. The division of Eurasia into two continents reflects East-West cultural, linguistic and ethnic differences which vary on a spectrum rather than with a sharp dividing line. The geographic border between Europe and Asia does not follow any state boundaries: Turkey, Russia, Azerbaijan, Georgia and Kazakhstan are transcontinental countries. France, Portugal, the Netherlands, Spain and the United Kingdom are also transcontinental in that the main portion is in Europe while pockets of their territory are located in other continents.