Bulgarian language, member of the South Slavic group of the Slavonic subfamily of the Indo-European family of languages (see Slavic languages). Bulgarian is the native tongue of some 9 million people, most of whom live in Bulgaria, where it is the official language. It is also spoken to some extent in bordering and nearby countries. Although the Bulgars were originally a Turkic-speaking people from Asia, they merged with the Slavic tribes whom they conquered in the 7th cent. AD in the territory of present-day Bulgaria and took over their Slavic language. Old Bulgarian is an alternate name for the literary and liturgical language of the 9th to 11th cent. AD that is usually called Old Church Slavonic (see Church Slavonic). From Old Church Slavonic, in Bulgaria, a later local form known as Bulgarian Church Slavonic evolved, which was current from the 12th to the 15th cent. The Turkish conquest of Bulgaria in 1396 seriously hampered the development of the Bulgarian language for several centuries.

After the Bulgarians achieved independence in 1878, a modern literary language based on the vernacular came into its own. Modern Bulgarian, which is generally said to date from the 16th cent., borrowed many words from Greek and Turkish during the period of Turkish domination; more recently it has borrowed words from Russian, French, and German. The Bulgarian language lacks definite rules for stress; therefore, the accent of every word must be learned individually. Unlike most other Slavic tongues, Bulgarian has a definite article. This is in the form of a suffix joined to the noun. Another difference between Bulgarian and most other Slavic languages is that Bulgarian has almost completely dropped the numerous case forms of the noun. It uses position and prepositions (like English) to indicate grammatical relationships in a sentence instead of cases (like Russian). Despite these differences, Bulgarian closely resembles the other Slavic languages, especially with regard to grammar. A modified form of the Cyrillic alphabet is used for writing Bulgarian.

See S. B. Bernshtein, Short Grammatical Sketch of the Bulgarian Language (tr. 1952); H. I. Aronson, Bulgarian Inflectional Morphophonology (1968); C. Rudin, Aspects of Bulgarian Syntax (1986).