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 orthography
Latvian orthography, historically, used a system based upon German phonetic principles, while the Latgalian dialect was written using Polish orthographic principles. The present-day Latvian orthography was developed by the Knowledge Commission of the Riga Latvian Association in 1908, approved the same year by the orthography commission under the leadership of Kārlis Mīlenbahs and Jānis Endzelīns. Its basis is the Latin script and it was introduced by law from 1920 to 1922 in the Republic of Latvia. For the most part it is phonetic in that it follows the language's pronunciation.
Today, the Latvian standard alphabet consists of 33 letters.
The modern standard Latvian alphabet uses 22 unmodified letters of the Latin alphabet. The Latvian alphabet lacks "Q", "W", "X" and "Y", but their names are "kū", "dubult vē", "iks" and "igrek". These letters are not used in writing foreign personal and geographical names, since in Latvian they are adapted to Latvian phonology, orthography, and morphology, e. g. "Džordžs Volkers Bušs" (George Walker Bush). However, these letters can be used in mathematics and sometimes in brand names. It adds a further eleven letters by adding diacritic marks to some letters. The vowel letters "A", "E", "I" and "U" can take a macron to show length, unmodified letters being short. The letters "C", "S" and "Z", that in unmodified form are pronounced , and respectively, can be marked with a caron. These marked letters, "Č", "Š" and "Ž" are pronounced , and respectively. The letters "Ģ", "Ķ", "Ļ" and "Ņ" are written with a cedilla or a small comma placed below (or, in the case of the lowercase "g", above). They are modified (palatalized) versions of "G", "K", "L" and "N" and represent the sounds , , and . Non-standard varieties of Latvian add extra letters to this standard set.