SUMMARY
The article discusses the question of the formal-grammatical status and semantics of the Russian adversative conjunction “zato” (eng. ‘but’) in its usage. According to a number of linguists, the conjunctional function of this formal word is not obvious. The semantics of the conjunction “zato” did not also receive a uniform description. The author shows that some linguists find in the conjunction “zato” the reflection of syncretism of different parts of speech (conjunction and adverb, conjunction and pronominal particle, etc.) or refuse to consider it as the conjunction at all. Besides, not all linguists agree that the semantics of compensation predominates in the use of the conjunction “zato”. The article presents a constructive experiment in which native speakers had to compose and write down a sentence with the word “zato”. It turned out that in the usage “zato” performs the function of an adversative conjunction or its component and has a semantic dominant – the meaning of compensation, indicating the transition to the positive part of the message. The presence of a semantic dominant in the conjunction “zato” gets a psycholinguistic explanation. According to the author, the development of a semantic dominant in the conjunction “zato” is connected with the development of its formal, actually grammatical meaning of compensation. In the experiment it is shown that in a number of sentences-reactions the conjunction “zato” expresses such semantic relations as comparative, comparative and adversative, and causal justification. However this semantic interpretation of the conjunction “zato”, not connected with the positive restriction, is poorly supported in the usage. In the experiment another regularity is also revealed: if the conjunction “zato” sometimes does not express the meaning of compensation, then the conjunctional complexes formed with its participation never lose this semantics. In addition, the article expressed a semantic hypothesis about the origin of the conjunctional complex “no zato” (Eng. ‘but’). The author believes that the need for creation of a complex marker of the compensatory relations has been caused, on the one hand, by the causal and adversative syncretism of the conjunction “zato”, and on the other hand, by the low-expressiveness of the all-adversative conjunction “no” as a marker of compensation.