infirmity vs frailness

infirmity and frailness both are nouns.

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

As nouns, infirmity and frailness are synonyms defined as:

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

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

infirmity (noun)	frailness (noun)
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)