brown rat vs Norway rat

brown rat and Norway rat both are nouns.

Word	Noun	Adjective	Verb	Adverb
brown rat	Yes	No	No	No
Norway rat	Yes	No	No	No

As nouns, brown rat and Norway rat are synonyms defined as:

Other synonyms of brown rat include Rattus norvegicus.

brown rat (noun)	Norway rat (noun)
common domestic rat; serious pest worldwide	common domestic rat; serious pest worldwide