The article describes the process of formation of students' lexical competence, in the process of which linguistic consciousness does not address to the entire volume of lexical meaning, but to the most general and necessary for understanding in speech context semantic components. Behind the semantic structure of a polysemantic word in the mental lexicon there is a flexible semantic cluster which is a set of nuclear most stable and frequent semantic features that eventually form in the linguistic consciousness of a native speaker and in one of its configurations participate in the process of decoding a specific contextual value.