The term sea refers to certain large bodies of water, but there is inconsistency as to its precise definition and application. Most commonly, a sea may refer to a large expanse of saline water connected with an ocean, but it is also used sometimes of a large saline lake that lacks a natural outlet, e.g. the Aral Sea. Colloquially, the term is used as a synonym for ocean. Additionally, large lakes, such as the Great Lakes, are occasionally referred to as inland seas.

International Hydrographic Organization

The International Hydrographic Organization (IHO) is the international authority that sets forth nomenclature and definition of bodies of water. The IHO's Limits of Oceans and Seas was first published in 1928, with its current working document the third edition published in 1953. A fourth draft edition was proposed in 1986 but has yet to be ratified due to outstanding issues such as the Sea of Japan naming dispute.

Nomenclature

Some bodies of water that are called "seas" are not actually seas; there are also some seas that are not called "seas". The following is an incomplete list of such potentially confusing names.

• The Sea of Galilee is a small freshwater lake with a natural outlet, which is called Lake Tiberias or Lake Kinneret on modern Israeli maps, but its original name remains in use.
• The Sea of Cortés is more commonly known as the Gulf of California.
• The Persian Gulf is a sea.
• The Dead Sea is actually a lake, as is the Caspian Sea.

Extraterrestrial seas

See also Extraterrestrial liquid water

Lunar maria are vast basaltic plains on the Moon that were thought to be bodies of water by early astronomers, who referred to them as "seas".

Liquid water may have existed on the surface of Mars in the distant past, and several basins on Mars have been proposed as dry sea beds. The largest is Vastitas Borealis; others include Hellas Planitia and Argyre Planitia.

Liquid water is thought to be present under the surface of several moons, most notably Europa.

Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than "seas".

Science

The term "sea" has also been used in quantum physics. Dirac sea is an interpretation of the negative energy states that comprises the vacuum.

See also

• Oceanography
• Inlet
• International Maritime Organization
• List of places on land with elevations below sea level
• Pole of inaccessibility: the locations farthest from any coastline
• Marine debris
• Sea level
• Sea level rise
• Sea salt
• Seven Seas