Slavic phonotactics is determined by two types of context: firstly, it observes the distributional restrictions attendant on the syllable model (these are discussed in the entry on syllable structure); secondly, it is determined by  restrictions linked to the immediate segmental environment. The latter is connected with assimilation and lenition processes, which are largely statistical in nature. This means that some of them, although common, are not obligatory. Voicing and devoicing of obs…