littoral zone vs sea-coast

littoral zone and sea-coast both are nouns.

Word	Noun	Adjective	Verb	Adverb
littoral zone	Yes	No	No	No
sea-coast	Yes	No	No	No

As nouns, sea-coast is a hypernym of littoral zone; that is, sea-coast is a word with a broader meaning than littoral zone:

Other hypernyms of littoral zone include coast, seacoast, seashore.

littoral zone (noun)	sea-coast (noun)
the region of the shore of a lake or sea or ocean	the shore of a sea or ocean