People

enemy

Source:*vorgъProto-Slaviccertain

Russian враг (South Slavic shape) beside Ukrainian во́рог (East Slavic pleophony) is the classic Church Slavonic doublet.

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English

enemy

Polish

wróg

vruk

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In all five languages

BCS script

Latin under Cyrillic

Russian
врагvrag
vrakChurch Slavonic
The native East Slavic во́рог survives in folk poetry.
Ukrainian
во́рогvoroh
ˈʋɔrɔɦinherited
Polish
wróg
vrukinherited
Czech
nepřítel
ˈnɛpr̝iːtɛldifferent word · Proto-Slavic *ne- + *prijatelь 'not-friend'
Bosnian-Croatian-Serbian
neprijateljнепријатељ
ˈneprijateʎdifferent word · Proto-Slavic *ne- + *prijatelь 'not-friend'
BCS vrag, the cognate of враг, means 'devil'.
English
enemy

Russian враг “enemy”Polish wróg “enemy”Czech vrah “murderer”Bosnian-Croatian-Serbian vrag “devil (colloquial)”
Czech 'enemy' is nepřítel, BCS neprijatelj; Russian 'murderer' is уби́йца, Polish morderca; Russian 'devil' is чёрт.