Name given to a large body of salt water that is smaller than an ocean

The answer is sea.

A sea is a body of salt water that is smaller than an ocean. Seas are usually also connected to an ocean. An example of a sea is the Mediterranean sea which is also connected to the (North) Atlantic ocean. A sea could also be viewed as an interconnected system of the salty oceanic waters on Earth.

Another body of salt smaller than an ocean is a salt lake; Lake Urmia in Iran being one example.