Fortochka

A Fortochka (Russian: фо́рточка; [ˈfortətɕkə]) is a small ventilation window. It usually spans the frame of one window pane and opens on hinges independently of the whole window. Fortochkas are in common use in Russia, other post-Soviet states (Ukrainian: кватирка, kvatyrka), and Finland (Finnish: tuuletusikkuna).

A fortochka can be used for ventilation during traditionally cold winters, when opening a whole window would be impractical for heat conservation purposes.