lower rank vs lowness

lower rank and lowness both are nouns.

Word	Noun	Adjective	Verb	Adverb
lower rank	Yes	No	No	No
lowness	Yes	No	No	No

As nouns, lowness is a hypernym of lower rank; that is, lowness is a word with a broader meaning than lower rank:

lower rank: the state of being inferior
lowness: a position of inferior status; low in station or rank or fortune or estimation

Other hypernyms of lower rank include low status, lowliness.

lower rank (noun)	lowness (noun)
the state of being inferior	the quality of being low; lacking height
	a low or small degree of any quality (amount or force or temperature etc.)
	a feeling of low spirits
	a position of inferior status; low in station or rank or fortune or estimation