feebleness vs cachexia

feebleness and cachexia both are nouns.

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

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

feebleness: 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 feebleness include asthenia, astheny, cachexy, wasting, sickliness.

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