Oceania is a region centered on the islands of the tropical Pacific Ocean. Opinions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific (ethnologically divided into the subregions of Melanesia, Micronesia, and Polynesia) to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago. The term is sometimes used more specifically to denote a continent comprising Australia and proximate islands, or biogeographically as a synonym for either the Australasian ecozone (Wallacea and Australasia) or the Pacific ecozone (Melanesia, Polynesia, and Micronesia apart either from New Zealand or from mainland New Guinea)
Asia is generally defined as comprising the eastern four-fifths of Eurasia. It is located to the east of the Suez Canal and the Ural Mountains, and south of the Caucasus Mountains (or the Kuma-Manych Depression) and the Caspian and Black Seas. It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean and on the north by the Arctic Ocean.
Given its size and diversity, Asia - a toponym dating back to classical antiquity - "is more a cultural concept" incorporating diverse regions and peoples than a homogeneous physical entity Asia differs very widely among and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties and government systems.
