Tkachenko, Orest [Ткаченко, Орест; Tkačenko], b 10 December 1925 in Kharkiv. Linguist; son of Borys Tkachenko. He studied at Kharkiv University (1945–7) and Kyiv University (1947–50) and completed his graduate work in Slavic linguistics under Leonid Bulakhovsky at the Institute of Linguistics of the Academy of Sciences of the Ukrainian SSR (1950–3, doctorate in 1982). After joining the institute as a researcher, he chaired the Terminological Commission of the Ukrainian Committee of Slavists (1965–8) and helped compile the dictionary of Slavic linguistic terminology. Tkachenko has written articles in the fields of Slavic, Finno-Ugric, Romance, and Indo-European linguistics, sociolinguistics, and interlinguistics (Esperanto); on Ukrainian language stability; and on Oriental studies in Ukraine. His monographs (in Russian) deal with the comparative-historical phraseology of the Slavic languages and the Finno-Ugric languages (1979), the Meri language (1985), and the theory of the linguistic substratum (1989). He is also the coauthor of a book in Ukrainian on the comparative-historical study of the Slavic languages (1966) and a coeditor and coauthor of the Academy of Sciences of the Ukrainian SSR’s Ukrainian etymological dictionary (7 vols, 1982–).

[This article originally appeared in the Encyclopedia of Ukraine, vol. 5 (1993).]