in its primary sense, denotes Alternation a succession 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 alternations can be rung on five bells, multiply the numbers 1, 2, 3, 4, 5, 6, continually into one another; and the last product gives the number of changes.