invalid vs unsound

invalid is a noun but unsound is not a noun.

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

invalid (noun)	unsound (noun)
someone who is incapacitated by a chronic illness or injury

invalid (adjective)	unsound (adjective)
having no cogency or legal force	not sound financially
no longer valid	not in good condition; damaged or decayed
	suffering from severe mental illness
	containing or based on a fallacy
	physically unsound or diseased
	of e.g. advice

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