User:Saul/algebra
From Organic Design wiki
Combinations and Permutations
Permutations/Pick
A permutation is a sequence where the order does matter.
This is often notated by n pick r where n is the data set - say 40 lotto balls and r is the selection count - say 8 balls.
Combinations/Choose
A combination is a sequence where the order does NOT matter.
This is often notated by n choose r - these mean the same thing as in pick.