Definition:Factorial

Definition
Let $n \in \Z_{\ge 0}$ be a positive integer.

Also known as
While the canonical vocalisation of, for example, $4!$ is $4$ factorial, it can often be found referred to as $4$ bang or (usually by schoolchildren) $4$ shriek.

Some mathematicians prefer $4$ gosh.

Also see

 * Definition:Gamma Function: the extension to the complex plane


 * Definition:Rising Factorial
 * Definition:Falling Factorial


 * Equivalence of Definitions of Factorial