Jonas Juška (Žarėnai, 1815 – Kazan, 1886), linguist, attended the Kražiai gymnasium (where Valančius was one of his teachers), studied classical philology at the University of Harkov (1840-44), and had a teaching career in various Russian postings; he died in Kazan in 1886 and together with his brother Antanas (1819–1880), whose notable collections of folk songs he aided and helped see through the press, was reinterred in Lithuania, in 1990.

Stimulated by a meeting with Sreznevskij (1852), Juška undertook the linguistic study of Lithuanian, developing contacts at Kazan with the authoritative linguist at the university there, J.N. Baudouin de Courtenay, a former student of Schleicher and Sreznevskij, among others. With his support, three volumes of Lithuanian folk songs collected by Antanas appeared in 1880-82; until Jonas’s death, the three collaborated on a Lithuanian-Polish-Russian dictionary which began to appear in 1897.

In addition to being his brother’s collaborator on folk song and lexicographical material, Jonas Juška undertook linguistic work on the basis of Schleicher’s Litauische Grammatik (1856). His Kalbos lietuviško liežuvio (“Languages of the Lithuanian tongue”, 1861) was one of the first systematic scholarly attempts to distinguish Lithuanian dialects, of which four were identified on phonetic grounds: Samogitian, Prussian Lithuanian, Ariogallian, and Eastern Lithuanian. Juška proposed that everyone use their own dialect in writing, albeit with a common orthography. In addition, Juška devised a Lithuanian alphabet mixing Latin and Russian characters (used in Litovskie narodnie pesni, “Lithuanian folk songs”, 1867). Most of his works (such as a Lithuanian-Sanskrit dictionary) remained unpublished.