witness vs eyewitness

witness and eyewitness both are nouns.

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

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

witness: a close observer; someone who looks at something (such as an exhibition of some kind)
eyewitness: a spectator who can describe what happened

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

witness (noun)	eyewitness (noun)
testimony by word or deed to your religious faith	a spectator who can describe what happened
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)	eyewitness (verb)
be a witness to	be present at an event and see it with one's own eyes
perceive or be contemporaneous with