Proto-Slavic *prostъ

→ Belarusian просты (inherited)

→ Bulgarian прост (inherited)

→ Czech prostý (inherited)

→ Czech Prostějov (derived)

→ Old Church Slavonic простъ (inherited)

→ Lower Sorbian pšosty (inherited)

→ Polish prosty (inherited)

→ Romanian prost (derived)

→ Russian простой (inherited)

→ Serbo-Croatian prost (inherited)

→ Serbo-Croatian прост (inherited)

→ Slovene prost (derived)

→ Ukrainian простий (inherited)