testimony vs witness

testimony and witness both are nouns.

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

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

Other hyponyms of testimony include declaration, attestation, affidavit, subornation.

testimony (noun)	witness (noun)
a solemn statement made under oath	testimony by word or deed to your religious faith
an assertion offering firsthand authentication of a fact	someone who sees an event and reports what happened
something that serves as evidence	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

testimony (verb)	witness (verb)
	be a witness to
	perceive or be contemporaneous with