eyewitness vs witness

eyewitness and witness both are nouns.

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

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

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

Other hypernyms of eyewitness include looker, spectator, viewer, watcher.

As verbs, witness is a hypernym of eyewitness; that is, witness is a word with a broader meaning than eyewitness:

eyewitness (noun)	witness (noun)
a spectator who can describe what happened	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

eyewitness (verb)	witness (verb)
be present at an event and see it with one's own eyes	be a witness to
	perceive or be contemporaneous with