Proto-Slavic *pętъkъ

→ Belarusian пятніца (derived)

→ Czech pátek (inherited)

→ Kashubian piątk (inherited)

→ Lower Sorbian pětk (inherited)

→ Upper Sorbian pjatk (inherited)

→ Hungarian péntek (cognate)

→ Macedonian петок (inherited)

→ Polish piątek (inherited)

→ Slovak piatok (inherited)

→ Slovene petek (inherited)

→ Silesian piōntek (inherited)