Difference between an ocean and a sea

Leave it to the National Oceanic and Atmospheric Administration to help us with our terminology:

Many people use the terms ‘ocean’ and ‘sea’ interchangeably when speaking about the ocean, but there is a difference between the two terms when speaking of geography (the study of the Earth’s surface).

Seas are smaller than oceans and are usually located where the land and ocean meet. Typically, Seas are found on the margins of the ocean and are partially enclosed by land. An example is the Bering Sea being part of the Pacific Ocean. However, the Sargasso Sea is an exception, as it is defined only by ocean currents.