How were the Eastern Balts different from the Western Balts?

The classification of Baltic peoples into "Western" and "Eastern" groups is a traditional linguistic and ethnic distinction, though scholars note that these terms are somewhat inaccurate when applied to the entirety of the Baltic population, particularly those groups that left no written records.1

The Western Balts consisted primarily of the Old Prussians and the Yotvingians (or Suduvians). Linguistically, these groups were very closely related to one another.1

The Eastern Balts comprised the Lithuanians, Latvians, Selonians, Semigallians, and Curonians. The protolanguage of this group began to split into distinct languages, such as Lithuanian and Latvian, around the 7th century. While Curonian is sometimes viewed as a transitional language between the East and West Baltic groups, the other Eastern Baltic tribes developed their own linguistic identities during this period.12

Beyond these groups, there existed other Baltic populations—sometimes referred to as "D-Balts"—who lived further east near the upper reaches of the Dnieper River and were assimilated by Slavs between the 7th and 14th centuries.312