Last name Sinjak (Sinjak 
, Синяк 
) , in all the world, is quite a rare cognomen. The family name Sinjak is characteristic of Belarus, where it is quite a common surname, Ukraine, where it is quite a rare surname, and Kazakhstan, where it is a rare surname. In absolute terms, it most frequently occurs in Eastern Europe, particularly Ukraine, Belarus, and Russia. Much less frequently, Sinjak is the forename as well as the last name.