5) what is the technical difference between a \sea\ and an \ocean\?

Brief Explanations:

A sea is usually a smaller, partially - enclosed body of salt - water, often bordered by land and connected to an ocean. An ocean is a vast, continuous body of salt - water that covers a large part of the Earth's surface. Seas can be marginal seas (e.g., the Mediterranean Sea which is connected to the Atlantic Ocean) or inland seas (like the Caspian Sea which is land - locked but was historically connected to an ocean). Oceans are the major water bodies of the planet, such as the Pacific, Atlantic, Indian, Arctic, and Southern Oceans.

Answer:

A sea is a smaller, often partially - enclosed body of salt - water, usually bordered by land and connected to an ocean. An ocean is a vast, continuous body of salt - water covering a large part of the Earth's surface.