trigger vs set off

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

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

As verbs, trigger and set off are synonyms defined as:

Other synonyms of trigger include activate, actuate, spark, spark off, touch off, trigger off, trip.

trigger (noun)	set off (noun)
an act that sets in motion some course of events
lever that activates the firing mechanism of a gun
a device that activates or releases or causes something to happen

trigger (verb)	set off (verb)
release or pull the trigger on	cause to burst with a violent release of energy
put in motion or move to act	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