In math, we write a combination like this:
In plain language, this represents the number of possible combinations when you choose elements from a collection of elements. The subscript indicates that the expression represents a combination where order does not matter. See the permutation notation for when order matters.
In general, to express choose combinations we write:
To calculate the number of combinations see this formula.
The number of permutations of r items chosen from n total items is written as the two values stacked inside parentheses with a subscript p.