tiredness vs exhaustion

tiredness and exhaustion both are nouns.

Word	Noun	Adjective	Verb	Adverb
tiredness	Yes	No	No	No
exhaustion	Yes	No	No	No

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

tiredness: temporary loss of strength and energy resulting from hard physical or mental work
exhaustion: extreme fatigue

Other hyponyms of tiredness include asthenopia, eyestrain, jet lag, grogginess, logginess, loginess, senioritis.

tiredness (noun)	exhaustion (noun)
temporary loss of strength and energy resulting from hard physical or mental work	the act of exhausting something entirely
	serious weakening and loss of energy
	extreme fatigue