The official language is Bulgarian. It is based on the Cyrillic alphabet rather than the Latin alphabet.
The Cyrillic alphabet is also used in Russian and several other languages.
Аа, Бб, Вв, Гг, Дд ............
English is most commonly used with a very high percentage of the population being able to speak and write in English. Moreover in tourist destinations one can find menus, hotel forms and signs in English.
Furthermore French and German languages are also an option especially among the population above 30 years of age.