Lithuanian belongs to the Baltic branch of the Indo-European family. Most Baltic languages are extinct, including the tongues of prūsai (Prussian), jotvingiai (Jotvingian), kuršiai (Curonian), žiemgaliai (Semigallian), and sėliai (Selonian). The only Baltic languages preserved and used to date are Lithuanian and Latvian, which supposedly drifted apart somewhere around the 7th century.
Researchers of Indo-European languages say Lithuanian is the most archaic of all the living Indo-European tongues. In this respect it compares to the earliest Indo-European texts written 2500-3000 years ago.
- Lithuanian has preserved the opposition of long and short vowels, floating accent, etc.
- Lithuanian has a highly archaic grammatical structure. It still employs the early schemes of word building and inflexion where case, person, and other grammatical categories are expressed through word endings, and has preserved the old declension patterns.
- The vocabulary of the Lithuanian language contains numerous words inherited from the protolanguage of Indo-Europeans.