jet lag vs tiredness

jet lag and tiredness both are nouns.

Word	Noun	Adjective	Verb	Adverb
jet lag	Yes	No	No	No
tiredness	Yes	No	No	No

As nouns, tiredness is a hypernym of jet lag; that is, tiredness is a word with a broader meaning than jet lag:

jet lag: fatigue and sleep disturbance resulting from disruption of the body's normal circadian rhythm as a result of jet travel
tiredness: temporary loss of strength and energy resulting from hard physical or mental work

Other hypernyms of jet lag include fatigue, weariness.

jet lag (noun)	tiredness (noun)
fatigue and sleep disturbance resulting from disruption of the body's normal circadian rhythm as a result of jet travel	temporary loss of strength and energy resulting from hard physical or mental work