A sea is smaller than an ocean. Seas are located where the land and ocean meet. The sea is a part of the ocean that is partially enclosed by land.
There are four major oceans in the world. They are the Pacific, the Indian, the Arctic and the Atlantic. A fifth ocean, the Southern, also exists. The oceans of the world comprise 71 percent of the Earth's surface. Seas may be classified based on their degree of enclosure by land and their connection to a larger body of water. Marginal seas are partially enclosed by land. Mediterranean seas are mostly enclosed by land and have limited ability to share a current with an adjoining ocean or larger sea. Seas may also be epeiric or regional.