add up vs tot

add up is not a noun while tot is a noun.

Word	Noun	Adjective	Verb	Adverb
add up	No	No	Yes	No
tot	Yes	No	Yes	No

As verbs, add up and tot are synonyms defined as:

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

add up (noun)	tot (noun)
	a young child who is just beginning to walk
	a small amount (especially of a drink)

add up (verb)	tot (verb)
determine the sum of	determine the sum of
be reasonable or logical or comprehensible
to measure up to in kind or quality
add up in number or quantity