hap vs set off

hap is a noun but set off is not a noun.

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

hap (noun)	set off (noun)
an accidental happening

hap (verb)	set off (verb)
come to pass	cause to burst with a violent release of energy
	set in motion or cause to begin
	direct attention to, as if by means of contrast
	provoke or stir up
	put in motion or move to act
	depart for someplace
	make up for