black calla vs arum

black calla and arum both are nouns.

Word	Noun	Adjective	Verb	Adverb
black calla	Yes	No	No	No
arum	Yes	No	No	No

As nouns, arum is a hypernym of black calla; that is, arum is a word with a broader meaning than black calla:

black calla: ornamental plant of Middle East cultivated for its dark purple spathe
arum: any plant of the family Araceae; have small flowers massed on a spadix surrounded by a large spathe

Other hypernyms of black calla include aroid.

black calla (noun)	arum (noun)
ornamental plant of Middle East cultivated for its dark purple spathe	any plant of the family Araceae; have small flowers massed on a spadix surrounded by a large spathe
	starch resembling sago that is obtained from cuckoopint root