The cosmology of the ancient Greeks contained a river flowing around the outer rim of the world, the domain of the god Oceanus. As the European worldview stretched out beyond the Pillars of Hercules, it became more and more apparent that this "river" was a lot larger than the Mediterranean Sea, than the "known world".
Various regions of the World Ocean, separated by
continents or climactic barriers such as the
Equator, have their different characters.
1Geographers occasionally divide the two largest oceans at the
Equator, as these bodies of water have completely different characters between the
Northern and
Southern Hemispheres. The definition of particular oceans is controlled by the
International Hydrographic Organization, at least for its member nations.