sum vs sum total

sum and sum total both are nouns.

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

As nouns, sum and sum total are synonyms defined as:

Other synonyms of sum include summation.

sum (noun)	sum total (noun)
the whole amount	the final aggregate
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

sum (verb)	sum total (verb)
determine the sum of
be a summary of