foulness vs aroma

foulness and aroma both are nouns.

Word	Noun	Adjective	Verb	Adverb
foulness	Yes	No	No	No
aroma	Yes	No	No	No

As nouns, aroma is a hypernym of foulness; that is, aroma is a word with a broader meaning than foulness:

Other hypernyms of foulness include odor, odour, olfactory property, scent, smell.

foulness (noun)	aroma (noun)
the attribute of having a strong offensive smell	any property detected by the olfactory system
(of weather) the badness of the weather	a distinctive odor that is pleasant
a state characterized by foul or disgusting dirt and refuse
disgusting wickedness and immorality