necessity vs essential

necessity and essential both are nouns.

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

As nouns, necessity and essential are synonyms defined as:

Other synonyms of necessity include necessary, requirement, requisite.

necessity (noun)	essential (noun)
anything indispensable	anything indispensable
the condition of being essential or indispensable

necessity (adjective)	essential (adjective)
	basic and fundamental
	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