sum up vs repeat

sum up is not a noun while repeat is a noun.

Word	Noun	Adjective	Verb	Adverb
sum up	No	No	Yes	No
repeat	Yes	No	Yes	No

As verbs, repeat is a hypernym of sum up; that is, repeat is a word with a broader meaning than sum up:

Other hypernyms of sum up include ingeminate, iterate, reiterate, restate, retell.

sum up (noun)	repeat (noun)
	an event that repeats

sum up (verb)	repeat (verb)
give a summary (of)	happen or occur again
determine the sum of	to say, state, or perform again
be a summary of	to say again or imitate
	make or do or perform again
	repeat an earlier theme of a composition
	do over