unsound vs invalid

unsound is not a noun while invalid is a noun.

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

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

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not in good condition; damaged or decayed	no longer valid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

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