Addition

Any two numbers can be added together. The idea of addition is based on combining two sets. If I have a set of five pens, and a set of two pens, I can combine them into a set of seven pens. This may be written symbolically using the plus sign.

$5+2=7\text{five plus two equals seven}.$

The outcome of the addition is called sum. Thus, the sum of five and two is seven.

Arithmetic

The follow table shows the addition of numbers up to ten.

Table of addition

0	1	2	3	4	5	6	7	8	9
1	2	3	4	5	6	7	8	9	10
2	3	4	5	6	7	8	9	10	11
3	4	5	6	7	8	9	10	11	12
4	5	6	7	8	9	10	11	12	13
5	6	7	8	9	10	11	12	13	14
6	7	8	9	10	11	12	13	14	15
7	8	9	10	11	12	13	14	15	16
8	9	10	11	12	13	14	15	16	17
9	10	11	12	13	14	15	16	17	18