The exclamation mark or exclamation point is a punctuation mark usually used after an interjection or exclamation to indicate strong feelings or high volume (shouting), and often marks the end of a sentence. Example: “Watch out!”
In mathematics, the factorial of a positive integer n, denoted by n!, is the product of all positive integers less than or equal to n.
The character is encoded in Unicode as U+0021 ! exclamation mark (HTML: !).