Western Empire vs Western Roman Empire

Western Empire and Western Roman Empire both are nouns.

Word	Noun	Adjective	Verb	Adverb
Western Empire	Yes	No	No	No
Western Roman Empire	Yes	No	No	No

As nouns, Western Empire and Western Roman Empire are synonyms defined as:

Western Empire and Western Roman Empire: the western part after the Roman Empire was divided in 395; it lasted only until 476

Western Empire (noun)	Western Roman Empire (noun)
the western part after the Roman Empire was divided in 395; it lasted only until 476	the western part after the Roman Empire was divided in 395; it lasted only until 476