A rational number is any number that can be expressed as the quotient or fraction p/q of two integers, a numerator p (must be definite) and a non-zero denominator q. Since q may be equal to 1, every integer is a rational number.
. But in case of root 2 the value is not definite. That is 1.414.......
numerator must be a definite value for rational numbers. But root 2 is not definite. Therefore root 2 is irrational number.