Integers : All natural numbers, their negatives and 0 are called integers.

Whole numbers : All natural numbers and 0 are called whole numbers.

Rational numbers : The numbers which can be expressed in the form p/q,where p and q are integers and q not equal to 0, are called rational numbers.

Irrational numbers : Any real number which cannot be expressed in the form p/q, where p and q are integers and q not equal to 0, are called irrational numbers.

Real numbers : Both rational numbers and irrational numbers together are known are real numbers.

Absolute value of real number : ( Modulus ) The non negative value of a number without regarding its sign.