inanition vs lethargy

inanition and lethargy both are nouns.

Word	Noun	Adjective	Verb	Adverb
inanition	Yes	No	No	No
lethargy	Yes	No	No	No

As nouns, inanition and lethargy are synonyms defined as:

inanition and lethargy: weakness characterized by a lack of vitality or energy

Other synonyms of inanition include lassitude, slackness.

inanition (noun)	lethargy (noun)
exhaustion resulting from lack of food	weakness characterized by a lack of vitality or energy
weakness characterized by a lack of vitality or energy	inactivity; showing an unusual lack of energy
	a state of comatose torpor (as found in sleeping sickness)