summarise vs sum

summarise is not a noun while sum is a noun.

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

As verbs, summarise and sum are synonyms defined as:

Other synonyms of summarise include sum up, summarize.

summarise (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

summarise (verb)	sum (verb)
give a summary (of)	determine the sum of
be a summary of	be a summary of