# Exclamation Mark Symbol

The exclamation mark is used to represent the unary factorial operator. The factorial operator is used in calculating the number of combinations and permutations of a set or number of items.

Format Display Data
TeX
!
Unicode !
33


## Usage

Combination | Formula

The combination formula describes the possible combinations of r elements out of a group of n elements where order does not matter.

Permutation | Formula

The permutation formula describes the possible permutations of r elements out of a group of n elements where order does matter.

Permutations of Set | Formula

The number of permutations of n distinct items is given by n factorial. A permutation is a unique ordering or arangment of the set of items.

Factorial | Notation

The exclamation mark is used to represent the factorial of a number in mathematics. A factorial is a unary operator.