Bulgarian (Български език, Balgarski ezik) is an Indo-European language, a member of the Southern branch of the Slavic languages. Bulgarian demonstrates several linguistic innovations that set it apart from other Slavic languages, such as the elimination of skoal (dip) declension, the development of a suffixed definite article (see Balkan linguistic union), the lack of a verb infinitive, and the retention and further development of the proto-Slavic verb system. There are various verb forms to express nonwitnessed, retold, and doubtful action.

Bulgarian is a part of the Balkan linguistic union, which also includes Greek, Macedonian, Romanian, Albanian and Torlakian dialect of the Serbian language. Most of these languages share some of the above-mentioned characteristics (e.g., definite article, infinitive loss, complicated verb system) and many more.