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.
Latvian language
During the Soviet occupation (1940–1991), the policy of Russification greatly affected the Latvian language. Throughout this period, many Latvians and Latvia’s other ethnicities faced deportation and persecution. A massive immigration from the Soviet republics of Russia, Ukraine, Belarus and others followed, largely as a result of Stalin's plan to integrate Latvia and the other Baltic republics into the Soviet Union by means of Russian colonization. As a result, the proportion of the ethnic Latvian population within the total population was reduced from 80% in 1935 to 52% in 1989. In Soviet Latvia, most of the immigrants who settled in the country did not learn Latvian. Today, Latvian is the mother tongue of more than 60% of the country's population.