While there are technically only five oceans in the world, the term "seven seas" was coined in ancient literature and divided the oceans into the Arctic, North Atlantic, South Atlantic, North Pacific, South Pacific, Indian and Southern Oceans. Today, the five named oceans include the Atlantic, Pacific, Indian, Arctic, and Antarctic Oceans, and the term "seven seas" is no longer widely used.
In historical Greek literature, where the term "seven seas" is thought to have first appeared, the seven seas included the Aegean, Adriatic, Mediterranean, Black, Red, and Caspian seas. The Persian Gulf was also included as a sea, though it is technically not one. Once North America was explored by Europeans, the term referred to a new division of seas that included the Arctic, Atlantic, Indian, Pacific, Mediterranean, Caribbean and the Gulf of Mexico.
While these oceans all form one global ocean, the boundaries of the oceans have changed over time for historical, cultural, geographical, and scientific reasons. The newest of the oceans is the Antarctic Ocean, which had its boundaries proposed by the International Hydrographic Organization in 2000, but not all countries involved agreed and the boundaries have not yet been ratified. Before this time, the Antarctic Ocean was called the Southern Ocean.