of necessity vs needs

of necessity and needs both are adverbs.

Word	Noun	Adjective	Verb	Adverb
of necessity	No	No	No	Yes
needs	No	No	No	Yes

As adverbs, of necessity and needs are synonyms defined as:

Other synonyms of of necessity include inevitably, necessarily.

of necessity (adverb)	needs (adverb)
in such a manner as could not be otherwise	in such a manner as could not be otherwise