1sum 
/ˈsʌm/ noun
plural sums /ˈsʌm/ noun 1 [count] : an amount of money
▪ They spent large/considerable sums (of money) repairing the house. ▪ We donated a small sum (of money) to the charity. ▪ The sellers were asking for a modest sum. ▪ I paid the sum of $500. — see also lump sum 2 [count] a : the result of adding two or more numbers together
▪ The sum of 5 and 7 is 12.
b : a simple problem in mathematics — usually plural ▪ schoolchildren doing sums 3 [singular] : the whole amount of something
▪ Working odd summer jobs has been the sum of my experience so far. [=has been all the experience I've had so far] — see also sum total
▪ They spent large/considerable sums (of money) repairing the house. ▪ We donated a small sum (of money) to the charity. ▪ The sellers were asking for a modest sum. ▪ I paid the sum of $500. — see also lump sum
▪ The sum of 5 and 7 is 12.
b : a simple problem in mathematics — usually plural ▪ schoolchildren doing sums
▪ Working odd summer jobs has been the sum of my experience so far. [=has been all the experience I've had so far] — see also sum total
in sum 1 : as a brief statement of the most important information in a piece of writing or speech
▪ In sum [=in summary], we need a better public health-care system. 2 : in a few words
▪ The movie was, in sum [=in short], entertaining as well as educational.
▪ In sum [=in summary], we need a better public health-care system.
▪ The movie was, in sum [=in short], entertaining as well as educational.
sum and substance
: the general or basic meaning of something said or written
▪ What is the sum and substance [=gist] of the argument?
▪ What is the sum and substance [=gist] of the argument?
sum of its parts
◊Something that is greater/better/more than the sum of its parts is better or more effective as a team, combination, etc., than you would expect it to be when you look at the different parts that form it.
▪ The team lacks standout players, but it has proved to be greater than the sum of its parts.
▪ The team lacks standout players, but it has proved to be greater than the sum of its parts.
— see also zero-sum game
