brown rat vs Rattus norvegicus

brown rat and Rattus norvegicus both are nouns.

Word	Noun	Adjective	Verb	Adverb
brown rat	Yes	No	No	No
Rattus norvegicus	Yes	No	No	No

As nouns, brown rat and Rattus norvegicus are synonyms defined as:

brown rat and Rattus norvegicus: common domestic rat; serious pest worldwide

Other synonyms of brown rat include Norway rat.

brown rat (noun)	Rattus norvegicus (noun)
common domestic rat; serious pest worldwide	common domestic rat; serious pest worldwide