Bulgarian is classified as a Slavic language of the southern group, which also includes Macedonian, Serbo-Croatian, and Slovenian. Old Bulgarian, also known as Old Church Slavonic, was the first Slavic language fixed in writing (9th century). For this purpose, two Bulgarian monks, Cyril and Methodius, created a new alphabet, based partly on the Greek, that became known as the Cyrillic alphabet. Both the grammar and the vocabulary of modern Bulgarian show Turkish, Greek, Romanian, and Albanian influences.
In November 1991, the government made Turkish an optional subject four times weekly in schools in predominantly Turkish regions.