The Cyrillic script is an alphabetic writing system employed across Eastern Europe, North and Central Asian countries. It is based on the Early Cyrillic, which was developed in the First Bulgarian Empire during the 9th century AD at the Preslav Literary School. It is the basis of alphabets used in various languages, past and present, in parts of Southeastern Europe and Northern Eurasia, especially those of Slavic origin, and non-Slavic languages influenced by Russian. , around 252 million people in Eurasia use it as the official alphabet for their national languages. About half of them are in Russia. Cyrillic is one of the most used writing systems in the world. Cyrillic is derived from the Greek uncial script, augmented by letters from the older Glagolitic alphabet, including some ligatures. These additional letters were used for Old Church Slavonic sounds not found in Greek. The script is named in honor of the two Byzantine brothers, Saints Cyril and Methodius, who created the Glagolitic alphabet earlier on. Modern scholars believe that Cyrillic was developed and formalized by early disciples of Cyril and Methodius. With the accession of Bulgaria to the European Union on 1 January 2007, Cyrillic became the third official script of the European Union, following the Latin and Greek scripts.