essential vs must

essential and must both are nouns.

Word	Noun	Adjective	Verb	Adverb
essential	Yes	Yes	No	No
must	Yes	Yes	No	No

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

Other hyponyms of essential include desideratum, need, want.

essential (noun)	must (noun)
anything indispensable	the quality of smelling or tasting old or stale or mouldy
	grape juice before or during fermentation
	a necessary or essential thing

essential (adjective)	must (adjective)
basic and fundamental	highly recommended
defining rights and duties as opposed to giving the rules by which rights and duties are established
being or relating to or containing the essence of a plant etc
of the greatest importance
absolutely necessary; vitally necessary