in its primary sense, denotes a alternation succeeding by turns.

ALTERNATION is sometimes used to express the different changes or alterations of orders in any number of things proposed. This is also called permutation, &c., and is easily found by a continual multiplication of all the numbers, beginning at unity. Thus, if it be required to know how many changes or alterations can be rung on six bells, multiply the numbers 1, 2, 3, 4, 5, 6, continually into one another; and the last product gives the number of changes.