You should know that numbers are generally classified as real and imaginary. Under the real numbers, they are further classified into rational and irrational numbers. Under rational numbers, these include fractions and integers. Irrational numbers are in decimal forms that cannot be converted to fractions. Therefore, the difference between the two is that: -1.96312.. is a real, irrational number while √(-5) is imaginary. There is no value for a root of a negative number.