What is the difference beteen a sea and a gulf?

The primary difference between the two terms is one of encasing.  A "sea" is "The continuous body of salt water covering most of the earth's surface, especially this body regarded as a geophysical entity distinct from earth and sky." In its virtue of being continuous, it is not easily encased, as it   For example, the Arabian Sea feeds into the Indian Ocean, and while it is bordered by India, the Coast of Africa, and the Arabian Peninsula, it is wide and feeds outward to the larger body of the Indian Ocean.  Contrast this with the definition of a gulf, which is "A large area of a sea or ocean partially enclosed by land, especially a long landlocked portion of sea opening through a strait."  In this understanding, the gulf feeds into a sea or ocean, primarily because it is encased by lands in a close proximity.  For example, the Persian Gulf is narrowly fit in between the Arabian Peninsula and Iran.  At the same time, it feeds into the Arabian Sea.  The difference between the two is that the narrow and encased gulf feeds into the wide sea.