rankness vs body odour

rankness and body odour both are nouns.

Word	Noun	Adjective	Verb	Adverb
rankness	Yes	No	No	No
body odour	Yes	No	No	No

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

Other hyponyms of rankness include B.O., body odor.

rankness (noun)	body odour (noun)
the attribute of having a strong offensive smell	malodorousness resulting from a failure to bathe
the property of producing abundantly and sustaining vigorous and luxuriant growth