kaffir boom vs erythrina

kaffir boom and erythrina both are nouns.

Word	Noun	Adjective	Verb	Adverb
kaffir boom	Yes	No	No	No
erythrina	Yes	No	No	No

As nouns, erythrina is a hypernym of kaffir boom; that is, erythrina is a word with a broader meaning than kaffir boom:

kaffir boom: small semi-evergreen broad-spreading tree of eastern South Africa with orange-scarlet flowers and small coral-red seeds; yields a light soft wood used for fence posts or shingles
erythrina: any of various shrubs or shrubby trees of the genus Erythrina having trifoliate leaves and racemes of scarlet to coral red flowers and black seeds; cultivated as an ornamental

Other hypernyms of kaffir boom include coral tree.

As nouns, erythrina is a hypernym of kaffir boom; that is, erythrina is a word with a broader meaning than kaffir boom:

kaffir boom: small semi-evergreen tree of South Africa having dense clusters of clear scarlet flowers and red seeds
erythrina: any of various shrubs or shrubby trees of the genus Erythrina having trifoliate leaves and racemes of scarlet to coral red flowers and black seeds; cultivated as an ornamental

Other hypernyms of kaffir boom include coral tree.

kaffir boom (noun)	erythrina (noun)
small semi-evergreen broad-spreading tree of eastern South Africa with orange-scarlet flowers and small coral-red seeds; yields a light soft wood used for fence posts or shingles	any of various shrubs or shrubby trees of the genus Erythrina having trifoliate leaves and racemes of scarlet to coral red flowers and black seeds; cultivated as an ornamental
small semi-evergreen tree of South Africa having dense clusters of clear scarlet flowers and red seeds