An Irrational number is any real number which is not rational. That means an irrational number cannot be represented as a simple fraction. It has no perfect value and can be expressed as a non recurring decimal. Let us know about its history in this section.At the time of the Greeks (from about the fifth century), people use whole positive numbers and Fractions. People didn't use negative numbers or Irrational Numbers. The Greeks were the first people to determine the need for irrational number.
From the early history of irrational numbers this is tied up with Pythagoras' Theorem, which was known before the time of the Greeks and was not actually invented by Pythagoras. But the Greeks were the first one to realize the significance of it for the development of numbers.
Irrational numbers were first discovered by Hippasus a greek mathematician which suprised even pythagorus. He was drowned as he was protested by many for this. The famous proof is the Square root of 2 is irrational which means it cannot be written as a fraction and square root of 2 was the first number to be proved irrational.
It is also said that irrationality concept was suggested by Indian mathematician Manava in 7th century BC, but there is no proper evidence for that.