This is the 10087th most frequent Polish word.
białoruski
Belarusian.
In this sentence, "białoruski" is in the form "białoruskiego," referring to the Belarusian language, which is distinguished as an object in a statement.
Studenci uczą się języka białoruskiego na kursie.
Students are learning the Belarusian language in the course.
Here, "białoruski" is used as an adjective ("białoruska") describing the noun "potrawa" (dish), indicating its national origin.
To jest tradycyjna białoruska potrawa.
This is a traditional Belarusian dish.
In this context, "białoruski" is used as an adjective to describe the noun "sportowiec" (athlete), specifying origin and identity.