The purpose of the monograph is to introduce the development of natural languages ​ ​ and language changes, to discuss the merits and disadvantages of the main theories and concepts regarding their causes and mechanisms, as well as to present the author's theses that allow him to outline his own view on these issues. The author's conclusions are the fruit of his many years of research in the field of historical linguistics, the theory of linguistic changes, as well as language typology and contrasting linguistics. The book is addressed to a wide range of readers interested in these issues, primarily philologists and linguists.