1. Numbers 1, 2, 3……., which are used for counting are called Natural numbers and are denoted by N.

2. 0 when included with the natural numbers form a new set of numbers called Whole number denoted by W

3. -1,-2,-3……………..-are the negative of natural numbers.

4. The negative of natural numbers, 0 and the natural number together constitutes integers denoted by Z.

5. Commutative law of addition: If a and b are two real numbers then, a + b = b + a

6. Irrational numbers are the numbers which are non-terminating and non-repeating.

7. Rational and irrational numbers together constitute Real numbers and it is denoted by R.

8. Equivalent rational numbers (or fractions) have same (equal) values when written in the simplest form.

9. Terminating fractions are the fractions which leaves remainder 0 on division.

10. Recurring fractions are the fractions which never leave a remainder 0 on division.