Latgalian language
Originally Latgalians were a tribe living in modern Vidzeme and Latgale. It is thought that they spoke the Latvian language, which later spread through the rest of modern Latvia, absorbing features of the Old Curonian, Semigallian, Selonian and Livonian languages. The Latgale area became politically separated during the Polish–Swedish wars, remaining part of the Polish–Lithuanian Commonwealth as the Inflanty Voivodeship, while the rest of Latvians lived in lands dominated by Baltic German nobility. Both centuries of separate development and the influence of different prestige languages likely contributed to the development of modern Latgalian as distinct from the language spoken in Vidzeme and other parts of Latvia.
Latvian grammar
Unlike, for example, Romance languages where conjugation classes are assigned based on thematic vowels (e.g., "-are", "-ere", "-ire" forming, respectively, the 1st, 2nd and 3rd conjugation in Italian) Latvian verbs are classified in conjugations regardless of whether they end in "-āt", "-ēt", "-īt", "-ot" or "-t". The classification depends on whether the verb stem has a thematic vowel, and if so, whether it is retained in present tense.