# '!' In Maths

I heard somewhere that '!' in maths is 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 *1 or something. And you can read 1! as 1BANG. I think. Is that true? If not, can someone explain this to me?

Note by Pola Forest
4 years, 1 month ago

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$$n!$$ is read as '$$n$$ factorial' or 'factorial $$n$$'.

If $$n$$ is a non-negative integer, then

$n!=1, \text{when}\ n=0$

$n!=n\times (n-1)!\ \text{when} \ n>1$

In other words, if $$n$$ is an integer greater than $$0$$, then $$n!=n\times (n-1)\times (n-2)\times \cdots \times 2\times 1$$. And $$0!=1$$ by definition.

I hope this helps!

- 4 years, 1 month ago