hear vs witness

hear is not a noun while witness is a noun.

Word	Noun	Adjective	Verb	Adverb
hear	No	No	Yes	No
witness	Yes	No	Yes	No

hear (noun)	witness (noun)
	testimony by word or deed to your religious faith
	someone who sees an event and reports what happened
	a close observer; someone who looks at something (such as an exhibition of some kind)
	(law) a person who attests to the genuineness of a document or signature by adding their own signature
	(law) a person who testifies under oath in a court of law

hear (verb)	witness (verb)
get to know or become aware of, usually accidentally	be a witness to
perceive (sound) via the auditory sense	perceive or be contemporaneous with
receive a communication from someone
listen and pay attention
examine or hear (evidence or a case) by judicial process