harebell vs bellflower

harebell and bellflower both are nouns.

Word	Noun	Adjective	Verb	Adverb
harebell	Yes	No	No	No
bellflower	Yes	No	No	No

As nouns, bellflower is a hypernym of harebell; that is, bellflower is a word with a broader meaning than harebell:

harebell: perennial of Northern Hemisphere with slender stems and bell-shaped blue flowers
bellflower: any of various plants of the genus Campanula having blue or white bell-shaped flowers

Other hypernyms of harebell include campanula.

harebell (noun)	bellflower (noun)
perennial of Northern Hemisphere with slender stems and bell-shaped blue flowers	any of various plants of the genus Campanula having blue or white bell-shaped flowers
sometimes placed in genus Scilla