witness vs doer

witness and doer both are nouns.

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

As nouns, doer is a hypernym of witness; that is, doer is a word with a broader meaning than witness:

Other hypernyms of witness include actor, worker.

witness (noun)	doer (noun)
testimony by word or deed to your religious faith	a person who acts and gets things done
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

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