Square root of two
The square root of the number two is
Explanation
The ratio between the side and the diameter of a square cannot be written by any pair of whole numbers. So they are incomparable. Because of this √2 is called an irrational number. On your calculator you can see that √2 = 1.4142135... and it lies on the number line between 1 and 2.
1 √2 1
Additional information
In the pythagorean school this was regarded as a proof of demonstation, that integers are not qualified to describe the real world.