happen vs spark

happen is not a noun while spark is a noun.

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

happen (noun)	spark (noun)
	merriment expressed by a brightness or gleam or animation of countenance
	a momentary flash of light
	a small fragment of a burning substance thrown out by burning material or by friction
	electrical conduction through a gas in an applied electric field
	a small but noticeable trace of some quality that might become stronger

happen (verb)	spark (verb)
come to pass	put in motion or move to act
come into being; become reality	emit or produce sparks
happen, occur, or be the case in the course of events or by chance
come upon, as if by accident; meet with
chance to be or do something, without intention or causation