[n] the arithmetic operation of summing; calculating the sum of two or more numbers; "the summation of four and three gives seven"; "four plus three equals seven"
[n] a concluding summary (as in presenting a case before a law court)
[n] the final aggregate; "the sum of all our troubles did not equal the misery they suffered"
[n] (physiology) the process whereby multiple stimuli can produce a response (in a muscle or nerve or other part) that one stimulus alone does not produce