What name is given to the open ocean?

An ocean is just a vast expanse or quantity of water. As a result of this explanation it seems that there is no difference between an ocean and a sea.The Word Ocean derives from the Latin 'oceanus' and the Greek 'okeanus' which was thought to be a great river or sea surrounding the disk of the Earth. Oceanus was the son of Uranus and Gaia. This comes from early times when only the large land masses of Europe and Africa were known and the Ocean was an endless river that flowed around them. In later times the name was 'ocean sea' and later still when exploration discovered even larger bodies of water did the term 'ocean sea' divide into 'sea' for smaller bodies of water and 'ocean' for the largest There are now five Oceans, Atlantic, Pacific, Indian, Arctic and Antarctic