SummaryOrder and disorderThe degree of order and of disorder are defined such that they are complementary and, each, vary between 0 and 1. Examples are given in problems of human life, of his community (with anarchistic and totalitarian extremes); also in thermodynamics (entropy) and information theory. In the latter problems the statistical quantityappears; it has quite the same meaning in both cases: the quantity of statistically weighted alternatives. The relation to entropy and to quantity of selective information is discussed. The degree of order 1 (degree of disorder 0) appears if this statistical quantity is 0, one of the p(i) being equal to 1 („frozen” or „pure” state). The degree of order 0 (degree of disorder 1) appears if this quantity is log n, all p(i) being equal to 1/n. The degree of disorder is equal toIn information theory the degree of order is identical i=1 with redundancy. Order/disorder problems in patterns are related to Mark off chains of higher order and are not discuss