irrational number – a number that cannot be written as a fraction. It is a decimal which is never ending

(pronounced ih-ra-shuh-nuhl)

To remember the meaning of irrational number, use the following mnemonic:

I have a rash on all (irrational) my body, the spots go on and on (never ending).

Unlike rational numbers like 0.5 `(1/2)` or 0.75 `(3/4)`, irrational numbers have decimal expansions that go on forever without repeating in a pattern.

Example 1

1.41421356………. Is an irrational number, and is also known as the surd $\sqrt{2}$

2.7370508075…… Is an irrational number, and is also known as the surd $\sqrt{3}$

3.333333333…….. Is rational as it can be turned into a fraction `1/3`

Example 2

The most famous irrational number is  $\pi =3.142$… on and on and on.