Synonyms for Summation (same or very similar meaning)
WordNet sense 1 (the final aggregate):
sum, sum totalWordNet sense 2 (a concluding summary (as in presenting a case before a law court)):
rundown, summing upWordNet sense 3 (the arithmetic operation of summing; calculating the sum of two or more numbers):
addition, plusFrom the ODE community, based on WordNetadd/edit