This monograph is devoted to a layer of language that has not previously been completely described in linguistics—particles. The first paragraph of the book (“Some introductory considerations”) emphasizes the fundamental difference between particles and what is commonly called particles. The author identifies the reasons for traditional linguistics' rejection of this linguistic layer. The role of particles in the formation of Indo-European paradigms is demonstrated. It is also shown that at earlier stages of existence the Slavic languages had much more similarities. Therefore, for example, Old Russian is closer to Old Church Slavonic (not only in composition, but also in “particle abundance”) than modern Russian. Finally, it is also significant that in one language particles are preserved only in phraseological units, while in others they are used freely. The works of classics of linguistics are widely used: F. Bopp, B. Delbrück, K. Brugmann, F. Specht and others, as well as works of the most recent years.