An irrational number is a number that cannot be expressed as a fraction, like Pi ------------------------------- The square root of 2 is irrational as it cannot be expressed as a fraction since the decimal never stops and never repeats. Same goes for the square root of 3, and 5 ------------------------------- Square root of 1 is rational as because the square root of 1 is 1, and the number 1 can be expressed as a fraction (1/1)