Why does order not matter when counting combinations?
In combinatorics, the distinction between permutations and combinations lies in whether the order of selection matters. A combination is defined specifically as a selection of objects from a set where order is not a factor.1
Order does not matter when counting combinations because the goal is to identify unique subsets rather than distinct sequences. In a permutation, the arrangement of items is considered significant; for example, selecting items A and B in that specific order (AB) is viewed as distinct from selecting them as BA.1
When counting combinations, however, these different arrangements are treated as a single, indistinguishable selection. Because any group of objects can be arranged in different ways, there are permutations for every unique combination. To account for this, the formula for combinations is derived by dividing the number of permutations by , effectively removing the influence of order from the final count.1