Real number
A real number is a number that falls on the real number line. It can have any value. Some examples of real numbers are:
, and so on. Numbers that are not real are 
, 
, 
, i.e. complex numbers, and quaternions.
The set of real numbers is denoted by 
. Commonly used subsets of the real numbers are the rational numbers (
), integers (
), natural numbers (
) and irrational numbers (sometimes, but not universally, denoted 
). The real numbers can also be divided between the algebraic numbers and trancendental numbers, although these two classes are best understood as subsets of the complex numbers.
