This is the 3970th most frequent French word.
biélorusse
Belarusian.
In this sentence, 'biélorusse' is used as an adjective to describe the genre or origin of the poetry, indicating it is Belarusian.
Elle a acheté un livre de poésie biélorusse.
She bought a book of Belarusian poetry.
Here, 'biélorusse' functions as an adjective modifying 'écrivain' (writer), specifying that the writer is from Belarus.
L'écrivain biélorusse a gagné un prestigieux prix littéraire.
The Belarusian writer won a prestigious literary award.
In this case, 'biélorusse' is used as a noun to refer to a person from Belarus, applied in its feminine form.