Arbitrary

Choices and actions are considered to be arbitrary when they are done not by means of any underlying principle or logic, but by whim or some decidedly illogical formula. For example, rearranging, for no reason, the letters of the alphabet so the letters appear in a staggered fashion (e.g. ac-bd-eg-fh). If there was a direct purpose in doing so, such as to make a better alphabet, then it would not be considered arbitrary.

Arbitrary decisions are not necessarily the same as random decisions. For instance, during the 1973 oil crisis, Americans were only allowed to purchase gasoline on odd-numbered days if their license plate was odd, and on even-numbered days if their license plate was even. The system was well-defined and not random in its restrictions; however, since license plate numbers have nothing to do with a person's fitness to purchase gasoline, it is still an arbitrary division of people. Similarly, schoolchildren are often organized by their surname in alphabetical order, a non-random yet still arbitrary method, at least in most cases where surnames are irrelevant.