niff vs stench

niff and stench both are nouns.

Word	Noun	Adjective	Verb	Adverb
niff	Yes	No	No	No
stench	Yes	No	No	No

As nouns, stench is a hypernym of niff; that is, stench is a word with a broader meaning than niff:

Other hypernyms of niff include fetor, foetor, malodor, malodour, mephitis, reek, stink.

niff (noun)	stench (noun)
an unpleasant smell	a distinctive odor that is offensively unpleasant