need vs lack

need and lack both are nouns.

Word	Noun	Adjective	Verb	Adverb
need	Yes	No	Yes	No
lack	Yes	No	Yes	No

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

Other hyponyms of need include deficiency, want, necessity.

need (noun)	lack (noun)
the psychological feature that arouses an organism to action toward a desired goal; the reason for the action; that which gives purpose and direction to behavior	the state of needing something that is absent or unavailable
anything that is necessary but lacking
a condition requiring relief
a state of extreme poverty or destitution

need (verb)	lack (verb)
have need of	be without
have or feel a need for	To be insufficiently prepared
require as useful, just, or proper