xerostomia vs dryness

xerostomia and dryness both are nouns.

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

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

xerostomia: abnormal dryness of the mouth resulting from decreased secretion of saliva
dryness: the condition of not containing or being covered by a liquid (especially water)

Other hypernyms of xerostomia include waterlessness, xerotes.

xerostomia (noun)	dryness (noun)
abnormal dryness of the mouth resulting from decreased secretion of saliva	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)