Byelorussia vs Belarus

Byelorussia and Belarus both are nouns.

Word	Noun	Adjective	Verb	Adverb
Byelorussia	Yes	No	No	No
Belarus	Yes	No	No	No

As nouns, Byelorussia and Belarus are synonyms defined as:

Byelorussia and Belarus: a landlocked republic in eastern Europe; formerly a European soviet

Other synonyms of Byelorussia include Belorussia, Byelarus, Republic of Belarus, White Russia.

Byelorussia (noun)	Belarus (noun)
a landlocked republic in eastern Europe; formerly a European soviet	a landlocked republic in eastern Europe; formerly a European soviet