Addition is the basic arithmetic operation often used while the others are multiplication, subtraction and division. The term addition counts the given numbers as together what we call adding. It is in fact the sum of given numbers.
If x and y are the given numbers. The addition formula is given by sum z given as,
z = x + y.
If $a_1$, $a_2$, $a_3$,........an are given numbers. The addition formula is given by,
Z = $a_1$ + $a_2$ + $a_3$ +........ + $a_n$.
Where z is the sum of the given numbers.