frailness vs cachexia

frailness and cachexia both are nouns.

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

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

frailness: the state of being weak in health or body (especially from old age)
cachexia: any general reduction in vitality and strength of body and mind resulting from a debilitating chronic disease

Other hyponyms of frailness include asthenia, astheny, cachexy, wasting, sickliness.

frailness (noun)	cachexia (noun)
the state of being weak in health or body (especially from old age)	any general reduction in vitality and strength of body and mind resulting from a debilitating chronic disease