nonessential vs adjunct

nonessential and adjunct both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonessential	Yes	Yes	No	No
adjunct	Yes	Yes	No	No

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

nonessential (noun)	adjunct (noun)
anything that is not essential	a construction that can be used to extend the meaning of a word or phrase but is not one of the main constituents of a sentence
	something added to another thing but not an essential part of it
	a person who is an assistant or subordinate to another

nonessential (adjective)	adjunct (adjective)
not of prime or central importance	of or relating to a person who is subordinate to another
	furnishing added support