This is the 6271st most frequent Polish word.
biegły
"Biegły" means "expert" or "proficient" in English.
The word biegły is used to refer to an expert with proficiency in a specific field.
On jest biegłym sądowym i często pomaga rozwiązywać sprawy.
He is a court expert and often helps to resolve cases.
Biegła is used as an adjective here, referring to someone being skilled or proficient in an activity.
Na przestrzeni lat stała się bardzo biegła w grze na pianinie.
Over the years, she became very proficient at playing the piano.
Biegłych is used in this sentence as an adjective to describe participants who are skilled or trained in running.