catch up vs come back

catch up and come back both are verbs.

Word	Noun	Adjective	Verb	Adverb
catch up	No	No	Yes	No
come back	No	No	Yes	No

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

catch up (verb)	come back (verb)
learn belatedly; find out about something after it happened	be restored
reach the point where one should be after a delay	go back to something earlier
	answer back
	even the score, in sports