A wave dashing on the shore
A wave hitting a breakwater in the Gulf of Santa Catalina.
Shipping in Singapore Harbour
Seas are important for human development and trade, as at Singapore, the world's busiest entrepôt.

A sea is a large body of salt water that is surrounded in whole or in part by land.[1][2][a] More broadly, "the sea" is the interconnected system of Earth's salty, oceanic waters—considered as one global ocean or as several principal oceanic divisions. The sea moderates Earth's climate and has important roles in the water cycle, carbon cycle, and nitrogen cycle. Although the sea has been traveled and explored since prehistory, the modern scientific study of the sea—oceanography—dates broadly to the British Challenger expedition of the 1870s.[3] The sea is conventionally divided into up to five large oceanic sections—including the International Hydrographic Organization's four named oceans[4] (the Atlantic, Pacific, Indian, and Arctic) and the Southern Ocean;[5] smaller, second-order sections, such as the Mediterranean, are known as seas.

Owing to the present state of continental drift, the Northern Hemisphere is now fairly equally divided between land and sea (a ratio of about 2:3) but the South is overwhelmingly oceanic (1:4.7).[6] Salinity in the open ocean is generally in a narrow band around 3.5% by mass, although this can vary in more landlocked waters, near the mouths of large rivers, or at great depths. About 85% of the solids in the open sea are sodium chloride. Deep-sea currents are produced by differences in salinity and temperature. Surface currents are formed by the friction of waves produced by the wind and by tides, the changes in local sea level produced by the gravity of the Moon and Sun. The direction of all of these is governed by surface and submarine land masses and by the rotation of the Earth (the Coriolis effect).

Former changes in sea levels have left continental shelves, shallow areas in the sea close to land. These nutrient-rich waters teem with life, which provide humans with substantial supplies of food—mainly fish, but also shellfish, mammals, and seaweed—which are both harvested in the wild and farmed. The most diverse areas surround great tropical coral reefs. Whaling in the deep sea was once common but whales' dwindling numbers prompted international conservation efforts and finally a moratorium on most commercial hunting. Oceanography has established that not all life is restricted to the sunlit surface waters: even under enormous depths and pressures, nutrients streaming from hydrothermal vents support their own unique ecosystem. Life may have started there and aquatic microbial mats are generally credited with the oxygenation of Earth's atmosphere; both plants and animals first evolved in the sea.

The sea is an essential aspect of human trade, travel, mineral extraction, and power generation. This has also made it essential to warfare and left major cities exposed to earthquakes and volcanoes from nearby faults; powerful tsunami waves; and hurricanes, typhoons, and cyclones produced in the tropics. This importance and duality has affected human culture, from early sea gods to the epic poetry of Homer to the changes induced by the Columbian Exchange, from burial at sea to Basho's haikus to hyperrealist marine art, and inspiring music ranging from the shanties in The Complaynt of Scotland to Rimsky-Korsakov's "The Sea and Sinbad's Ship" to A-mei's "Listen to the Sea". It is the scene of leisure activities including swimming, diving, surfing, and sailing. However, population growth, industrialization, and intensive farming have all contributed to present-day marine pollution. Atmospheric carbon dioxide is being absorbed in increasing amounts, lowering its pH in a process known as ocean acidification. The shared nature of the sea has made overfishing an increasing problem.


The interconnected system of the world's oceans and their various divisions.

Both senses of sea date to Old English; the larger sense has required a definite article since Early Middle English.[5] As the term has been applied over time, there are no sharp distinctions between seas and oceans, although seas are smaller and are usually bounded by land masses (and ones smaller scale than continents),[7] the singular standard exception being the Sargasso Sea, which is created by the four currents bounding what is termed the North Atlantic Gyre.[8](p90) Seas are generally larger than lakes and contain salt water. While the defining elements of size and being bounded are generally used, there is no formally accepted technical definition of "sea" among oceanographers.[b] In international law, the United Nations Convention on the Law of the Sea states that all the ocean is "the sea".[11][c]

Other Languages
Адыгэбзэ: Хы
Afrikaans: See
Alemannisch: Meer
አማርኛ: ባህር
العربية: بحر
aragonés: Mar
ܐܪܡܝܐ: ܝܡܐ
armãneashti: Amari
asturianu: Mar
Avañe'ẽ: Para
авар: Ралъад
Aymar aru: Lamara
azərbaycanca: Dəniz
تۆرکجه: دنیز
বাংলা: সাগর
Bân-lâm-gú: Hái
Basa Banyumasan: Segara
башҡортса: Диңгеҙ
беларуская: Мора
беларуская (тарашкевіца)‎: Мора
भोजपुरी: समुंद्र
Bikol Central: Dagat
български: Море
Boarisch: Meea
bosanski: More
brezhoneg: Mor
буряад: Тэнгис
català: Mar
čeština: Moře
corsu: Mare
Cymraeg: Môr
dansk: Hav
Deutsch: Meer
dolnoserbski: Mórjo
eesti: Meri
Ελληνικά: Θάλασσα
emiliàn e rumagnòl: Mèr
español: Mar
Esperanto: Maro
estremeñu: Mari
euskara: Itsaso
فارسی: دریا
Fiji Hindi: Samundar
føroyskt: Sjógvur
français: Mer
Frysk: See
furlan: Mâr
Gaeilge: Farraige
Gaelg: Mooir
Gàidhlig: Muir
galego: Mar
한국어: 바다
Hausa: Teku
հայերեն: Ծով
hornjoserbsce: Morjo
hrvatski: More
Ido: Maro
Ilokano: Baybay
Bahasa Indonesia: Laut
interlingua: Mar
Ирон: Денджыз
isiXhosa: Ulwandle
isiZulu: Ulwandle
íslenska: Sjór
italiano: Mare
עברית: ים
Basa Jawa: Segara
ಕನ್ನಡ: ಸಮುದ್ರ
къарачай-малкъар: Тенгиз
ქართული: ზღვა
қазақша: Теңіз
kernowek: Mor
Kiswahili: Bahari
коми: Саридз
Kongo: Kalunga
Kreyòl ayisyen: Lanmè
kurdî: Derya
Кыргызча: Деңиз
кырык мары: Тангыж
Ladino: Mar
лакку: Хьхьири
лезги: Гьуьл
ລາວ: ທະເລ
Latina: Mare
latviešu: Jūra
Lëtzebuergesch: Mier
lietuvių: Jūra
Limburgs: Zieë
lingála: Lombú
la .lojban.: xamsi
lumbaart: Mar
magyar: Tenger
मैथिली: समुन्द्र
македонски: Море
മലയാളം: കടൽ
मराठी: समुद्र
მარგალური: ზუღა
مصرى: بحر
مازِرونی: دریو
Bahasa Melayu: Laut
Baso Minangkabau: Lauik
Mìng-dĕ̤ng-ngṳ̄: Hāi
Mirandés: Mar
монгол: Тэнгис
မြန်မာဘာသာ: ပင်လယ်
Nāhuatl: Huēyātl
Nederlands: Zee
Nedersaksies: Zee
नेपाली: समुन्द्र
नेपाल भाषा: समुद्र
Napulitano: Mare
нохчийн: ХӀорд
norsk: Hav
norsk nynorsk: Hav
occitan: Mar
олык марий: Теҥыз
ଓଡ଼ିଆ: ସମୁଦ୍ର
oʻzbekcha/ўзбекча: Dengiz
ਪੰਜਾਬੀ: ਸਮੁੰਦਰ
پنجابی: سمندر
Papiamentu: Laman
ភាសាខ្មែរ: សមុទ្រ
Plattdüütsch: Meer
polski: Morze
português: Mar
Qaraqalpaqsha: Ten'iz
Ripoarisch: Meer
română: Mare
Romani: Derya
Runa Simi: Hatun qucha
русиньскый: Море
русский: Море
саха тыла: Байҕал
ᱥᱟᱱᱛᱟᱲᱤ: ᱫᱚᱨᱭᱟ
Scots: Sea
Seeltersk: See
shqip: Deti
sicilianu: Mari
Simple English: Sea
سنڌي: سمنڊ
slovenčina: More
slovenščina: Morje
Soomaaliga: Bad
کوردی: دەریا
српски / srpski: Море
srpskohrvatski / српскохрватски: More
Basa Sunda: Sagara
suomi: Meri
svenska: Hav
Tagalog: Dagat
தமிழ்: கடல்
tarandíne: Mare
татарча/tatarça: Диңгез
తెలుగు: సముద్రం
ไทย: ทะเล
тоҷикӣ: Баҳр
ತುಳು: ಕಡಲ್‍
Türkçe: Deniz
Türkmençe: Deňiz
українська: Море
اردو: بحیرہ
Vahcuengh: Haij
vèneto: Mar
vepsän kel’: Meri
Tiếng Việt: Biển
Võro: Meri
walon: Mer
West-Vlams: Zêe
Winaray: Dagat
Wolof: Géej
吴语: 大海
ייִדיש: ים
Zeêuws: Zeê
žemaitėška: Jūra
डोटेली: सागर
ГӀалгӀай: Форд
Kabɩyɛ: Teŋgu