happen vs go

happen is not a noun while go is a noun.

Word	Noun	Adjective	Verb	Adverb
happen	No	No	Yes	No
go	Yes	Yes	Yes	No

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

happen (noun)	go (noun)
	a board game for two players who place counters on a grid; the object is to surround and so capture the opponent's counters
	a usually brief attempt
	street names for methylenedioxymethamphetamine
	a time period for working (after which you will be relieved by someone else)

happen (adjective)	go (adjective)
	functioning correctly and ready for action

happen (verb)	go (verb)
come to pass	pass from physical life and lose all bodily attributes and functions necessary to sustain life
come into being; become reality	follow a certain course
happen, occur, or be the case in the course of events or by chance	progress by being changed
come upon, as if by accident; meet with	stop operating or functioning
chance to be or do something, without intention or causation	enter or assume a certain state or condition
	be abolished or discarded
	give support (to) or make a choice (of) one out of a group or number
	have a turn; make one's move in a game
	to be spent or finished
	be spent
	perform as expected when applied
	go through in search of something; search through someone's belongings in an unauthorized way
	change location; move, travel, or proceed, also metaphorically
	move away from a place into another direction
	begin or set in motion
	make a certain noise or sound
	follow a procedure or take a course
	stretch out over a distance, space, time, or scope; run or extend between two points or beyond a certain point
	have a particular form
	pass, fare, or elapse; of a certain state of affairs or action
	be in the right place or situation
	be the right size or shape; fit correctly or as desired
	be awarded; be allotted
	be or continue to be in a certain condition
	lead, extend, or afford access
	be ranked or compare
	blend or harmonize
	be sounded, played, or expressed
	be contained in
	continue to live and avoid dying