The numbers which have a non-terminating and non-repeating decimal expansion and cannot be represented in the form of pq ( q is not equal to '0') are known as
Irrational
An irrational number is a real number that cannot be expressed as a ratio of integers, i.e. as a fraction.
Therefore, irrational numbers, when written as decimal numbers, do not terminate, nor do they repeat.
√2, √3 are examples of irrational numbers.