occur vs come up

occur and come up both are verbs.

Word	Noun	Adjective	Verb	Adverb
occur	No	No	Yes	No
come up	No	No	Yes	No

As verbs, come up is a hyponym of occur; that is, come up is a word with a more specific, narrower meaning than occur:

occur (verb)	come up (verb)
come to pass	result or issue
come to one's mind; suggest itself	start running, functioning, or operating
to be found to exist	gather or bring together
	gather (money or other resources) together over time
	bring forth, usually something desirable
	come up, of celestial bodies
	come to the surface
	move toward, travel toward something or somebody or approach something or somebody
	move upward
	get something or somebody for a specific purpose
	originate or come into being
	be mentioned