feebleness vs asthenia

feebleness and asthenia both are nouns.

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

As nouns, asthenia is a hyponym of feebleness; that is, asthenia 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)
asthenia: an abnormal loss of strength

Other hyponyms of feebleness include astheny, cachexia, cachexy, wasting, sickliness.

feebleness (noun)	asthenia (noun)
the quality of lacking intensity or substance	an abnormal loss of strength
the state of being weak in health or body (especially from old age)