Irrational number, also known as infinite acyclic decimal, cannot be written as the ratio of two integers. If written in decimal form, there are infinitely many digits after the decimal point, which will not cycle.

Common irrational numbers include the square root, π and E (the latter two are transcendental numbers) of incomplete square numbers. Another feature of irrational numbers is the expression of infinite connected fractions. Pythagoras' disciple Hiberzos first discovered irrational numbers.

Rational numbers are composed of all fractions and integers, which can always be written as integers, finite decimals or infinite cyclic decimals, and can always be written as the ratio of two integers, such as 2 1/7.

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/kloc-Leonardo da Vinci, a famous Italian painter in the 0/5th century, called it an "irrational number", and Kepler, a German astronomer in the 0/7th century, called it an "indescribable number".

However, after all, the truth cannot be submerged, and it is "unreasonable" for the main Sect to obliterate the truth. People named this incommensurable quantity "irrational number" in memory of this respectable scholar Ebersus who devoted himself to truth-this is the origin of irrational number.

The mathematical crisis caused by irrational numbers continued until the second half of19th century. 1872, the German mathematician Dai Dejin started from the requirement of continuity, defined irrational numbers through the division of rational numbers, and established the theory of real numbers on a strict scientific basis, thus ending the era when irrational numbers were regarded as "irrational numbers" and the first great crisis in the history of mathematics that lasted for more than two thousand years.