black archangel vs Ballota nigra

black archangel and Ballota nigra both are nouns.

Word	Noun	Adjective	Verb	Adverb
black archangel	Yes	No	No	No
Ballota nigra	Yes	No	No	No

As nouns, black archangel and Ballota nigra are synonyms defined as:

black archangel and Ballota nigra: ill-smelling European herb with rugose leaves and whorls of dark purple flowers

Other synonyms of black archangel include black horehound, fetid horehound, stinking horehound.

black archangel (noun)	Ballota nigra (noun)
ill-smelling European herb with rugose leaves and whorls of dark purple flowers	ill-smelling European herb with rugose leaves and whorls of dark purple flowers