A number being added to another number is called an addend. The total of the numbers added together is called the sum.
Addition, and addends are the numbers being added.
An addend is a number or quantity to be added to another.
addition a number
Another number added to a number is the sum (total) of the two numbers.
you call is the sum
The two numbers that are being added are each called addends, and the result is called a sum.