Animals & plants

bird

Source:*pъticaProto-Slaviccertain

The weak yer after p vanished, leaving the unusual cluster pt- in every language.

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English

bird

Polish

ptak

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In all five languages

BCS script

Latin under Cyrillic

Russian
пти́цаptica
ˈptʲitsəinherited
Ukrainian
пти́цяptycja
ˈptɪtsʲainherited
птах, the cognate of Polish ptak, is just as common.
Polish
ptak
ptakdifferent word · Proto-Slavic *pъtakъ, from the same root as *pъtica
Czech
pták
ptaːkdifferent word · Proto-Slavic *pъtakъ, from the same root as *pъtica
Bosnian-Croatian-Serbian
pticaптица
ˈptitsainherited
English
bird