foulness vs odour

foulness and odour both are nouns.

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

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

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

foulness (noun)	odour (noun)
the attribute of having a strong offensive smell	any property detected by the olfactory system
(of weather) the badness of the weather	the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form
a state characterized by foul or disgusting dirt and refuse
disgusting wickedness and immorality