happen vs trip

happen is not a noun while trip is a noun.

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

happen (noun)	trip (noun)
	a journey for some purpose (usually including the return)
	an unintentional but embarrassing blunder
	a light or nimble tread
	a catch mechanism that acts as a switch
	an accidental misstep threatening (or causing) a fall
	an exciting or stimulating experience
	a hallucinatory experience induced by drugs

happen (verb)	trip (verb)
come to pass	get high, stoned, or drugged
come into being; become reality	put in motion or move to act
happen, occur, or be the case in the course of events or by chance	miss a step and fall or nearly fall
come upon, as if by accident; meet with	cause to stumble
chance to be or do something, without intention or causation	make a trip for pleasure