A boyar was a member of the highest rank of the feudal Bulgarian, Kievan, Moscovian, Wallachian and Moldavian and later, Romanian , second only to the ruling princes (in Bulgaria, tsars), from the 10th century to the 17th century. The rank has lived on as a surname in Russia, Ukraine and Romania, and in Finland, where it is spelled Pajari.
Also known as bolyar, the words various names in other languages include Bulgarian: боляр or болярин; Ukrainian: буй or боярин; Russian: боя́рин, tr. boyarin; IPA: [bɐˈjærʲɪn]; Romanian: boier, IPA: [boˈjer]; and Greek: βογιάρος,
The word is likely derived from the plural form of the Bulgarian title boila ("noble"), bolyare, which is attested in Bulgar inscriptions and rendered as boilades or boliades in the Greek of Byzantine documents. Multiple different derivation theories of the word have been suggested by scholars and linguists, such as it having possible roots from old Turkic: bai ("noble, rich"; cf. "bey") and är ("man, men"). Another possible etymology of the term it may come from the Romanian word "boi" (bulls); a rich man is an owner of bulls or "boier". The title entered Old Russian as быля (bylya, attested solely in The Tale of Igor's Campaign).