**Addition** is the mathematical process of putting things together, that is to say *joining*. With the addition of two numbers, the process may be thought of moving a certain distance in the positive direction. If one considers the following equation:

The plus sign or addition symbol ( + ) marks that addition is preformed on its adjacent numerals (**a** and **b**). **C** is called *the sum of a and b*. This equation may be calculated by moving

**a**,

**b**whole units in the positive direction.

## Computation

Taking in account the analogy from the previous section,

may be thought of as moving **3** in the positive direction by **4** units:

with may be counted to achieve the answer of **7**.

## Properties

- Addition is commutative:
- Addition is associative:
- Addition has an identity element: zero.

## Estimation

Addition sums are possible to be estimated. It is done by rounding off each addend to the nearest n significant figures (where n is a whole number), and adding both of the rounded numbers.