noun / verb
sum
SUM/sʌm/
The total obtained by bringing parts together.
The sum of the red and blue counters is five.

Etymology
Latin summa meant both “top” and “total.” The connection probably reflects the Roman practice of adding figures upward and writing the total at the top of the column.
In context
we're going to find the sum of the arithmetic series that we have on the screen now in order to get the answer we could simply use a calculator and add up the numbers
More examples
- We sum the monthly expenses to calculate our annual costs.
- A good team is more than the sum of its parts.
- Her final paragraph sums up the main points.
Forms
sum · sums · summed · summing
summation noun — The process of adding quantities together.