Dictionaries are one of the most valuable sources for historical and linguistic studies of the language. They allow you to document the role and place of certain language elements in the history of the culture of the people, fix lexemes in certain historical periods, indicate the relationship of different languages, show the mutual influence of different-structured language systems. At the same time, dictionaries are an indicator of linguistic modification, i.e., innovations that arise in a language under the influence of various socio-political, social, cultural factors, manifesting themselves as linguistic variability at different linguistic levels of the language, including lexicographic. Despite the fact that they are not special lexicographic sources in the field of synonymy, in the explanatory dictionaries of the Turkic languages a lot of synonymous lexemes are recorded, showing the harmonious development of the literary and colloquial language.  This study examines the lexical synonyms recorded in the Explanatory Dictionary of the Tatar Language (Tatar Telenen Anlatmali Suzlege, 2015) and the Academic Dictionary of the Bashkir Language (Academic Dictionary of Bashkir Language, 2012), as representatives of the Kipchak group of Turkic languages, which are considered in the linguistic aspect as components of a common Turkic lexical fund.  The relevance of the study is explained by the tasks of identifying the role of the activity of synonyms recorded in the studied dictionaries. The article presents materials reflecting the research experience of teachers of the Kazan Federal University together with colleagues from the Republic of Bashkortostan on the study of Turkic languages, including the Tatar and Bashkir languages in synchrony and in diachrony.  The purpose of this study is the lexico-semantic development of synonyms of the Tatar and Bashkir languages recorded in the explanatory dictionaries, relative to the vocabulary of the dictionary of Mahmud Kashgari “Divan lugat at-Turk”. In the course of the study, the authors studied the modern works of Russian and foreign authors on linguistics, philology; lexical material recorded in the explanatory dictionaries and dictionaries of synonyms of the Tatar and Bashkir languages is analyzed; comparisons of vocabulary and practical speech are made; The main trends in the development of vocabulary of the modern Tatar and Bashkir literary languages as representatives of Turkic linguistics are revealed.