An addition is the combination of two numbers to produce their sum. Calcute implements it using either the add function or, equivalently, the + (plus) operator.
add(11,222.33; 44,555.66) 55,777.99
11,222.33 + 44,555.66 55,777.99
In an addition, each value being added is called an "addend". The result of an addition is called the "sum".