aridness vs dryness

aridness and dryness both are nouns.

Word	Noun	Adjective	Verb	Adverb
aridness	Yes	No	No	No
dryness	Yes	No	No	No

As nouns, dryness is a hypernym of aridness; that is, dryness is a word with a broader meaning than aridness:

aridness: a deficiency of moisture (especially when resulting from a permanent absence of rainfall)
dryness: the condition of not containing or being covered by a liquid (especially water)

Other hypernyms of aridness include waterlessness, xerotes.

aridness (noun)	dryness (noun)
a deficiency of moisture (especially when resulting from a permanent absence of rainfall)	objectivity and detachment
	moderation in or abstinence from alcohol or other drugs
	the condition of not containing or being covered by a liquid (especially water)