Latvian language
Upper Latvian dialect is spoken in Eastern Latvia. It is set apart from rest of the Latvian by number of phonetic differences. The dialect has two main varieties – Selonian and Non-Selonian. There is a standard language, the Latgalian language, which is based on deep Non-Selonian varieties spoken in south of Latgale. The term "Latgalian" is sometimes also applied to all Non-Selonian varieties or even the whole dialect. However, it is unclear if it is accurate to use the term for any varieties besides the standard language. While the term may refer to varieties spoken in Latgale or by Latgalians, not all speakers identify as speaking Latgalian, for example, speakers of deep Non-Selonian varieties in Vidzeme explicitly deny speaking Latgalian.
Latvia
Several important cultural changes occurred during this time. Under Swedish and largely German rule, western Latvia adopted Lutheranism as its main religion. The ancient tribes of the Couronians, Semigallians, Selonians, Livs, and northern Latgallians assimilated to form the Latvian people, speaking one Latvian language. Throughout all the centuries, however, an actual Latvian state had not been established, so the borders and definitions of who exactly fell within that group are largely subjective. Meanwhile, largely isolated from the rest of Latvia, southern Latgallians adopted Catholicism under Polish/Jesuit influence. The native dialect remained distinct, although it acquired many Polish and Russian loanwords.