The present paper deals with the problem of interlingual equivalence in vocabulary, text translation and intercultural communication and proposes a novel approach to this problem based on ideas from prototype theory and field theory. Within this approach, interlingual equivalence is defined not as the relation between two lexemes, but as the relation between a lexeme and a semantic field. The first part of the paper thus provides a general description of the main types of corresponding semantic fields. The second part deals with the factors that generally serve as a basis for establishing equivalence relations between lexical units in systems of the languages being compared and in texts. Particular attention is paid to outlining the differences between these factors. Furthermore, the paper discusses peculiarities arising when establishing equivalence relations between utterances in interlingual communication. In certain communicative situations, equivalent utterances cannot be perceived as adequate forms of realisation of a speech act, which must be taken into account in order to avoid misunderstanding and communication failure. In this case, equivalence relations in communication often need to be replaced by relations of adequacy. The difference between equivalence and adequacy is discussed as well. The analysis is based on comparison of the lexical‐semantic spheres of English, German and Russian.