go through vs witness

go through is not a noun while witness is a noun.

Word	Noun	Adjective	Verb	Adverb
go through	No	No	Yes	No
witness	Yes	No	Yes	No

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

Other hyponyms of go through include experience, know, live, endure, suffer, meet, suffer, feel, enjoy, find, see, come.

go through (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

go through (verb)	witness (verb)
eat up completely, as with great appetite	be a witness to
apply thoroughly; think through	perceive or be contemporaneous with
undergo or live through a difficult experience