black art vs witchcraft

black art and witchcraft both are nouns.

Word	Noun	Adjective	Verb	Adverb
black art	Yes	No	No	No
witchcraft	Yes	No	No	No

As nouns, witchcraft is a hyponym of black art; that is, witchcraft is a word with a more specific, narrower meaning than black art:

black art: the belief in magical spells that harness occult forces or evil spirits to produce unnatural effects in the world
witchcraft: the art of sorcery

Other hyponyms of black art include witchery, bewitchment, enchantment, demonism, diabolism, Satanism, obiism.

black art (noun)	witchcraft (noun)
the belief in magical spells that harness occult forces or evil spirits to produce unnatural effects in the world	the art of sorcery