happen vs set off

happen and set off both are verbs.

Word	Noun	Adjective	Verb	Adverb
happen	No	No	Yes	No
set off	No	No	Yes	No

happen (verb)	set off (verb)
come to pass	cause to burst with a violent release of energy
come into being; become reality	set in motion or cause to begin
happen, occur, or be the case in the course of events or by chance	direct attention to, as if by means of contrast
come upon, as if by accident; meet with	provoke or stir up
chance to be or do something, without intention or causation	put in motion or move to act
	depart for someplace
	make up for