This is the 3427th most frequent French word.
bélarusse
Belarusian (relating to Belarus or its people, language, or culture).
Here, 'bélarusse' is used as a noun to refer to the Belarusian language, showing its role as the subject of the sentence.
La langue officielle en Bélarus est le bélarusse.
The official language in Belarus is Belarusian.
In this sentence, 'bélarusse' functions as an adjective, describing the nationality of my friend.
Mon ami est bélarusse et il m'a appris à dire bonjour en sa langue.
My friend is Belarusian and he taught me how to say hello in his language.
Here, 'bélarusses' is an adjective in plural form, modifying 'specialités' to indicate that the specialties originate from Belarus.