WordNet sense 1 (a quantity of money):

amount, amount of money, sum of money

WordNet sense 2 (a set containing all and only the members of two or more given sets):

join, union

WordNet sense 3 (the final aggregate):

summation, sum total

WordNet sense 4 (the choicest or most essential or most vital part of some idea or experience):

center, core, essence, gist, heart, kernel, marrow, meat, nitty-gritty, nub, pith, substance, inwardness, heart and soul

WordNet sense 5 (a quantity obtained by the addition of a group of numbers):

total

WordNet sense 6 (the whole amount):

aggregate, totality, aggregate

WordNet sense 7 (be a summary of):

summarize, summarise, sum up

WordNet sense 8 (determine the sum of):

add, tally, tot, summate, add up, tote up, tot up, add together