This article is devoted to the problem of enantiosemy - one of the most special phenomena in the lexical-semantic aspect of the Russian language. This sphere attracts the interest of many researchers but not yet sufficiently studied and determined by nonsystematic approach of the described object. Research of an enantiosemy as multi-sided and difficult linguistic unit demands studying of a wide range of the questions explaining its contradictory nature. So, the author suggests to approach not only from classic term, so-called enantiosemy (ENS), which means “intra-word antonymy” but also consider the terms of antagonym or contronym, reflecting their asymmetric feature of semantic polarity. The article analyses the category of ENS and the mechanisms of their formation and classifies 3 main types of ENS. Firstly, ENS with superficial negation, secondly, ENS with inversion of diathesis (agent - patient), thirdly, interlingual ENS with panchronic adoption. ENS may be the result of a semantic reconsideration of the word and a revision of connotation in individual word usage such as metonymy and metaphor (one of the typical mechanisms of ENS). Also, linguistic and extralinguistic factors function as mechanism of ENS and reflect the points of view of the participants (agens-patiens) of the communicative situation. ENS is, first of all, multi-temporal in nature, and their opposite meanings, associated with the same root (Proto-Slavic). This semantic syncretism can be traced at different diachronical and synchronical stages of Slavic language development. That’s why ENS is widely represented in colloquial speech, dialects, jargon and conspicuous for two opposite meaning in many Slavic languages. The author comes to a conclusion that the essence of ENS with its semantic ambiguity lies not in the occasional deviation from the norm, but in a realization of effective communicative strategy.