The book “Fundamentals of Phonology” by Nikolai Sergeyevich Trubetsky is a landmark work in the field of linguistics, which has become fundamental for the development of phonology as a science. Published in 1939, this work is still of interest to students, teachers, and researchers seeking a deeper understanding of the structure of language and its sound system. Trubetskoy, an outstanding Russian linguist and one of the founders of the Prague School, offers the reader a unique view of the phonological processes that shape the sound of words and their meaning. The book begins with a definition of phoneme, a key concept of phonology that Trubetskoy views as the minimal unit of the language's sound system. He analyzes in detail how phonemes interact with each other, forming complex sound structures, and how they affect language perception. The reader is immersed in the world of sounds, where each phoneme has its own characteristics and functions, and also plays an important role in communication. Trubetskoy not only describes theoretical aspects, but also supports his ideas with many examples from various languages, which makes the material accessible and understandable. This book will be of interest to students of linguistic faculties, as well as to those who are simply fond of languages and their structure. It is suitable for both beginners and more experienced researchers who want to deepen their knowledge in the field of phonology. If you are interested in topics such as phonetics, semantics or syntax, the “Fundamentals of phonology” will be a real discovery for you. Trubetskoy raises many important topics, including the relationship between sound and meaning, the role of context in the perception of phonemes, and the influence of phonological phenomena on the development of language. His work became the basis for many subsequent studies and theories, and without it it is impossible to imagine modern linguistics. The book not only introduces the reader to the basics of phonology, but also encourages reflection on how the sound structure of language affects our perception of the world. Trubetskoy’s style is clear and logical, which makes his ideas available to a wide audience. He masterfully combines theory with practice, which allows the reader not only to assimilate the material, but also to see its application in real life. It is also worth noting that Trubetskoy is the author of other well-known works, such as “Russian Language” and “Phonology”, which also deserve attention and can complement the understanding of his ideas. If you are looking for books on phonology, linguistics or just want to expand your horizons in language learning, Trubetskoy’s Fundamentals of Phonology is a must-read. This work will not only enrich your knowledge, but will also provide new ideas and perspectives that may prove useful in your future studies or research activities. Do not miss the opportunity to meet one of the greatest minds in the history of linguistics and discover the world of phonology, which may change your perception of language forever.