- The vast continuous body of salt water covering the greater part of the earth's surface and surrounding its land masses; the sea, esp. the open sea. (In early times, when only the one great mass of land, the Eastern hemisphere, with its islands, was known, the ocean was the ‘Great Outer Sea’ of boundless extent, everywhere surrounding the land, as opposed to the Mediterranean and other inland seas.)
- An immense or boundless expanse of something. Also (hyperbolically): a very great or indefinite quantity
An ocean (from Greek Ωκεανός, Okeanos (Oceanus)) is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (~3.61 X 1014 m2) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.
More than half of this area is over 3,000 metres (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Scientists estimate that 230,000 marine life forms of all types are currently known, but the total could be up to 10 times that number.