sea-coast vs tideland

sea-coast and tideland both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea-coast	Yes	No	No	No
tideland	Yes	No	No	No

As nouns, tideland is a hyponym of sea-coast; that is, tideland is a word with a more specific, narrower meaning than sea-coast:

Other hyponyms of sea-coast include litoral, littoral, littoral zone, sands, landfall, seaboard, seaside.

sea-coast (noun)	tideland (noun)
the shore of a sea or ocean	land near the sea that is overflowed by the tide