O·ka 
(ō-kä)
(ō-kä) A river, about 1,500 km (930 mi) long, of western Russia flowing north, east, and northeast to join the Volga River near Nizhny Novgorod.
- Indo-European root: konk-
- Indo-European root: koro-
- Indo-European root: kost-
- Indo-European root: kous-
- Indo-European root: krei-
- Indo-European root: kreus-
- Indo-European root: kreuə-
- Indo-European root: ksun
- Indo-European root: kwe
- Indo-European root: kwei-
- Indo-European root: kwei-
- Indo-European root: kweit-
- Indo-European root: kweiə-
- Indo-European root: kwel-
- Indo-European root: kwel-
- Indo-European root: kwen-
- Indo-European root: kwent(h)-
- Indo-European root: kwer-
- Indo-European root: kwes-
- Indo-European root: kwetwer-
- Indo-European root: kwo-
- Indo-European root: kwon-
- Indo-European root: kwrep-
- Indo-European root: kwr̥mi-
- Indo-European root: kwēt-