The Black Sea is an inland sea between southeastern Europe and Anatolia that is actually a distant arm of the Atlantic Ocean by way of the Mediterranean Sea. It is connected to the Mediterranean by the Bosporus and the Sea of Marmara, and to the Sea of Azov by the Strait of Kerch.

There is a net inflow of seawater through the Bosporus, 200 km? per year. There is an inflow of freshwater from the surrounding areas, especially central and middle-eastern Europe, totalling 320 km? per year. The most important river entering the Black Sea is the Danube.[1] The Black Sea has an area of 436,400 km?,[2] with a maximum depth of 2200 m. (7,218 ft.) [3]

Countries bordering on the Black Sea are Turkey, Romania, Bulgaria, Ukraine, Russia, and Georgia.[4] The Crimean peninsula is a Ukrainian autonomous republic.

Important cities along the coast include: Istanbul (urban area of 10,018,735) , Constanta (urban area of 401,613), Mangalia, Burgas, Varna (urban area of 357,752) , Odessa, Sevastopol, Yalta, Kerch, Novorossiysk (281,400), Sochi, Sukhumi, Poti, Batumi, Trabzon, Samsun and Zonguldak.

Modern names of the Sea are universally equivalents of the English name, "Black Sea", including Bulgarian Cherno more (×åðíî ìîðå), Georgian Shavi zghva (???? ????), Laz Ucha Zuga, or simply Zuga 'Sea', Romanian Marea Neagra, Russian Chyornoye More (׸ðíîå ìîðå), Turkish Karadeniz, Ukrainian Chorne More (×îðíå ìîðå), Ubykh /??a?a/. This name cannot be traced to an earlier date than the thirteenth century, but there are indications that it may be considerably older.

Strabo's Geography (1.2.10) reports that in antiquity, the Black Sea was often just called "the Sea" (pontos). For the most part, Graeco-Roman tradition refers to the Black Sea as the 'Hospitable sea', Euxeinos Pontos (???????? ??????). This is a euphemism replacing an earlier 'Inhospitable Sea', Pontos Axeinos, first attested in Pindar (early fifth century BCE). Strabo (7.3.6) thinks that the Black Sea was called "inhospitable" before Greek colonization because it was difficult to navigate, and because its shores were inhabited by savage tribes; and that the name was changed to "hospitable" after the Milesians had colonized, making it part of Greek civilization. It is also possible that the name Axeinos arose by popular etymology from an Iranian axsaina- 'dark'; the designation "Black Sea" may thus date from Antiquity. The reason for the name may be an ancient assignment of colours to the direction of the compass — black referring to the north, and red referring to the south. Herodotus on one occasion uses Red Sea and Southern Sea interchangeably.[5]

Another possible explanation comes from the colour of the Black Sea's deep waters. Being further north than the Mediterranean Sea and much less saline, the microalgae concentration is much richer, causing the dark colour. Visibility in the Black Sea is on average approximately five meters (5.5 yd), as compared to up to thirty-five meters (38 yd) in the Mediterranean.

One Bulgarian understanding of the name is that the sea used to be quite stormy. Some sources stipulate that it goes back to the time of Noah's Ark. The Black Sea deluge theory is based on that idea.

In naval science, the Black Sea is thought to have received its name because of its hydrogen sulfide layer that begins about 200 meters below the surface, and that ends all life from that point downward.