Proto-Slavic *slabъ

→ Belarusian слабы (inherited)

→ Bulgarian слаб (inherited)

→ Czech slabý (inherited)

→ Old Church Slavonic слабъ (inherited)

→ Lower Sorbian słaby (inherited)

→ Macedonian слаб (inherited)

→ Polish słaby (inherited)

→ Russian слабый (inherited)

→ Serbo-Croatian слаб (inherited)

→ Slovak slabý (inherited)

→ Ukrainian слабий (inherited)