The number of possible ways to choose permutations from total items is denoted using two parentheses with the variables and . A subscript is included to indicate that the expression represents permutations where *order does matter* as opposed to combinations where order does not matter. Typically, the notation is used in an expression like this:

In plain language, this represents the total number of permutations from choosing items from a collection of items. See combinations for where order does not matter.

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