The language written using the Cyrillic alphabet and serving as Bulgaria’s official language is Bulgarian.
Bulgarian is an Eastern South Slavic language spoken mainly in Bulgaria. It belongs to the Indo-European family and is closely related to Macedonian. Bulgarian uses its own version of the Cyrillic alphabet, whose modern form was standardized over centuries of linguistic and educational change.
The language’s written history reaches back to the medieval Slavic literary tradition. Old Church Slavonic, associated with the work of Saints Cyril and Methodius and their disciples, helped establish the Cyrillic-based culture of the First Bulgarian Empire. Bulgarian later developed distinctive features, including a suffixed definite article and the loss of most noun-case endings.
A common mix-up is confusing a language with its script: Cyrillic is the writing system, while Bulgarian is the language. Russian, Ukrainian, Serbian and Macedonian also use Cyrillic, but they are separate languages. Since 2007, Bulgarian has also been one of the official languages of the European Union.