The aim of the article is to describe when and in what form the term "monopoly" appeared in the theory. First, attention is paid to A.
Smith's classical political economy and the neoclassical binary model of competition and monopoly presented by A. Marshall.
Joan V. Robinson's model of imperfect competition and Edward H.
Chamberlin's model of monopolistic competition of 1933 are groundbreaking in the field of economic theory. The article not only highlights the elements that were adopted from Marshall and Pigou of the Cambridge Neoclassical School and are common to both theories, but also emphasizes the aspects in which the two approaches by Robinson and by Chamberlin differ and highlights their contribution for economic theory and competition law.