Ocean
An
ocean (from Ancient Greek Ὠκεανός
(Okeanos); the World Ocean of classical antiquity) is a body of saline water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean, which occupies two-thirds of planet's surface. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word
sea is often used interchangeably with "ocean" in American English but, strictly speaking, a sea is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land. Earth is the only planet that is known to have an ocean (or any large amounts of open liquid water). Saline water covers approximately 72% of the planet's surface (~3.6×108 km2) and is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of the Earth's surface. The ocean contains 97% of the Earth's water, and oceanographers have stated that only 5% of the World Ocean has been explored. The total volume is approximately 1.