malodour vs stench

malodour and stench both are nouns.

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

As nouns, malodour and stench are synonyms defined as:

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

malodour (noun)	stench (noun)
a distinctive odor that is offensively unpleasant	a distinctive odor that is offensively unpleasant