The article is one of the author's publications devoted to the modern linguistics language. The article is devoted to the problems of identity of modern basic linguistic categories - synchronism and diachronism, their prototypes which were presented by F. de Saussure in his work "The course of general linguistics". The circumstances of this dichotomy appearance are surveyed. And different interpretations of these basic categories given in works by native and foreign linguists of the 20th century are presented.