frailty vs frailness

frailty and frailness both are nouns.

Word	Noun	Adjective	Verb	Adverb
frailty	Yes	No	No	No
frailness	Yes	No	No	No

As nouns, frailty and frailness are synonyms defined as:

frailty and frailness: the state of being weak in health or body (especially from old age)

Other synonyms of frailty include debility, feebleness, infirmity, valetudinarianism.

frailty (noun)	frailness (noun)
moral weakness	the state of being weak in health or body (especially from old age)
the state of being weak in health or body (especially from old age)