sum up vs sum

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

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

As verbs, sum up and sum are synonyms defined as:

Other synonyms of sum up include add, add together, add up, summate, tally, tot, tot up, total, tote up.

As verbs, sum up and sum are synonyms defined as:

Other synonyms of sum up include summarise, summarize.

sum up (noun)	sum (noun)
	the whole amount
	the choicest or most essential or most vital part of some idea or experience
	a quantity obtained by the addition of a group of numbers
	the final aggregate
	a set containing all and only the members of two or more given sets
	a quantity of money