Definition
Use sum in a sentence

I was asked by a child how many hours it would take to reach our destination. I said it would take three hours today, and four hours tomorrow. The sum of three and four is seven.

Mrs. Warner told us that in order to get full credit, we had to provide the correct sum of all of the numbers, as well as show the work we did to arrive at the answer.

Dan had passed out about one hundred flyers for his new service, but had found that the sum total of his efforts had amounted to zero.
Notable Quotes

Trust and Large Sums of Money"Where large sums of money are concerned, it is advisable to trust nobody."
http://www.businessdictionary.com/definition/sum.html