odour vs stank

odour and stank both are nouns.

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

As nouns, stank is a hyponym of odour; that is, stank is a word with a more specific, narrower meaning than odour:

odour: the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form
stank: A smell of genitals or sex

odour (noun)	stank (noun)
any property detected by the olfactory system	A smell of genitals or sex
the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form