scarceness vs rarity

scarceness and rarity both are nouns.

Word	Noun	Adjective	Verb	Adverb
scarceness	Yes	No	No	No
rarity	Yes	No	No	No

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

Other hyponyms of scarceness include dearth, paucity, infrequency, rareness.

scarceness (noun)	rarity (noun)
a small and inadequate amount	something unusual -- perhaps worthy of collecting
	a rarified quality
	noteworthy scarcity