Abstract
The article identifies changes in the development of the synonym system, the criteria that make up the synonym series. Since synonyms are the main factor in the development of vocabulary and the richness of language, they should be studied in close connection with human thinking, association and stereotyping. Therefore, methods of cognitive research of synonyms have been proposed. Absolute synonyms are conditional, because meaning is constantly replenished and changes with the development of society. Hence, this article aims to prove conclusion that words whose meaning are fundamentally similar cannot be eternal. While antonyms are clearly binary oppositions, synonyms do not have such strict binary relations. The article was written to clarify the statement that creating synonymic series requires at least two-digit words. Currently, synonyms are also formed in the language system through authentic use of equivalent borrowings from other languages. Synonyms-epithets and synonyms-metaphors are also formed in cognitive-pragmatic interest. By studying synonyms in modern language within the «nucleus-periphery» framework, it becomes possible to determine relations between genotype-phenotype, hyponym - hypernym. Moreover, according to the «associative chain», the order of words in a synonymic series is defined by their semantic proximity to the preceding reference word. The methods of distinguishing synonymic series by semantic, stylistic and usage shades were proposed. The difference between associated and non-associated synonyms-epithets was demonstrated. Problems in translating synonyms into another language, along with their possible solutions, were discussed.