fetidness vs odour

fetidness and odour both are nouns.

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

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

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

fetidness (noun)	odour (noun)
the attribute of having a strong offensive smell	any property detected by the olfactory system
	the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form