The principle of complementarity was formulated by Niels Bohr as one of the interpretative rules of quantum mechanics. It relates to such features of a quantum system which are mutually exclusive and at the same time complement one another. It turned out, however, that this principle has countless applications beyond the context of the quantum mechanics. The main purpose of this article is to analyze various contexts and aspects in which the idea of complementarity is introduced. Special attention will be paid to the issues that do not directly concern quantum physics.