occur vs trigger

occur is not a noun while trigger is a noun.

Word	Noun	Adjective	Verb	Adverb
occur	No	No	Yes	No
trigger	Yes	No	Yes	No

occur (noun)	trigger (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

occur (verb)	trigger (verb)
come to pass	release or pull the trigger on
come to one's mind; suggest itself	put in motion or move to act
to be found to exist