necessary vs want

necessary and want both are nouns.

Word	Noun	Adjective	Verb	Adverb
necessary	Yes	Yes	No	No
want	Yes	No	Yes	No

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

Other hyponyms of necessary include desideratum, must, need.

necessary (noun)	want (noun)
anything indispensable	a specific feeling of desire
	anything that is necessary but lacking
	a state of extreme poverty
	the state of needing something that is absent or unavailable

necessary (adjective)	want (adjective)
absolutely essential
unavoidably determined by prior circumstances

necessary (verb)	want (verb)
	wish or demand the presence of
	have need of
	hunt or look for; want for a particular reason
	feel or have a desire for; want strongly
	be without, lack; be deficient in