sea aster vs aster

sea aster and aster both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea aster	Yes	No	No	No
aster	Yes	No	No	No

As nouns, aster is a hypernym of sea aster; that is, aster is a word with a broader meaning than sea aster:

sea aster: a common European aster that grows in salt marshes
aster: any of various chiefly fall-blooming herbs of the genus Aster with showy daisylike flowers

sea aster (noun)	aster (noun)
a common European aster that grows in salt marshes	star-shaped structure formed in the cytoplasm of a cell having fibers like rays that surround the centrosome during mitosis
	any of various chiefly fall-blooming herbs of the genus Aster with showy daisylike flowers