null vs invalid

null and invalid both are nouns.

Word	Noun	Adjective	Verb	Adverb
null	Yes	Yes	No	No
invalid	Yes	Yes	Yes	No

null (noun)	invalid (noun)
a quantity of no importance; thing (object:), singular, negative pronoun; pronoun, thing, singular; quantifier: negative existential	someone who is incapacitated by a chronic illness or injury

null (adjective)	invalid (adjective)
lacking any legal or binding force	having no cogency or legal force
	no longer valid

null (verb)	invalid (verb)
	injure permanently
	force to retire, remove from active duty, as of firemen