Theory of Groups . Classics and Modernity . Mathematics" is an exciting and in-depth study of one of the most fundamental areas of mathematics, written by a team of authors, each of whom is an expert in their field. This book is not just a textbook, but a real encyclopedia of group theory, which covers both classical aspects and modern achievements in this field. The book begins with the basics of group theory, introducing the reader to the world of abstract algebra. Here you will find explanations of key concepts such as groups, subgroups, homomorphisms and isomorphisms, which are cornerstones for understanding more complex structures. The authors not only describe the theory, but also illustrate it with examples from various fields of science, such as physics, chemistry and computer science. This makes the material more accessible and interesting, allowing the reader to see how abstract concepts are applied in the real world. The book will be especially useful for students and teachers of mathematical faculties, as well as for anyone interested in algebra and its applications. If you are studying for a bachelor’s or master’s degree, or just want to deepen your knowledge in mathematics, this publication will become an indispensable assistant for you. It will be of interest to both novice mathematicians and those who already have experience in this field and want to expand their horizons. The topics raised in the book cover a wide range of issues, including group structure, simple group theorems, and current methods and approaches used in research. The authors emphasize the importance of group theory in various fields of science, showing how it serves as the basis for many other mathematical disciplines. The reader will be able to see how theoretical concepts are applied in practice, which makes the study of group theory not only fascinating, but also useful. The style of the authors is distinguished by clarity and accessibility, which makes it easy to assimilate even the most complex ideas. They use many illustrations and examples to make the material more visual. In addition, the book contains exercises and tasks that will help readers consolidate their knowledge and develop their skills. If you are looking for books on mathematics that will help you understand group theory, pay attention to such works as "Algebra" and. R. Shafarevich 's