Selonian was a language appertaining to the Baltic languages group of the Indo-European languages family. This language was spoken by the Selonians, who lived until the 15th century in Eastern Latvia and North-Eastern Lithuania. They were a small Baltic tribe (now extinct) and their neighbours were predominantly Slavs and the Selonian was probably had been influenced by Russians as we see in the place names.
After the Grand Duchy of Lithuania was established, it comprised all the minor tribes, including the Selonians, who were assimilated and in the next century lost their language that became extinct.
The traces of the Selonian language can be still found in the territories Selonians inhabited, especially in the accent and phonetics.
The Balticlanguages are a group of related languages belonging to the Indo-European language family and spoken mainly in areas extending east and southeast of the Baltic Sea in Northern Europe.
Historically the languages were spoken over a larger area: West to the mouth of the Vistula river in present-day Poland, at least as far East as the Dniepr river in present-day Belarus, perhaps even to Moscow, perhaps as far South as Kiev.
Language kinship is generally determined by the identification of linguistic innovations that are held in common by two languages or groups.
The Lithuanian language is a highly inflected language in which the relationships between parts of speech and their roles in a sentence are expressed by numerous flexions.
The most common are the illative, which still is used, mostly in spoken language, and the allative, which survives in the standard language in some idiomatic usages.