This is the 4142nd most frequent Portuguese word.
russo
"Russo" means "Russian" in English.
In this sentence, 'russo' is used as a noun representing a person from Russia.
O russo que conheci ontem é muito simpático.
The Russian I met yesterday is very friendly.
Here, 'russo' is used as an adjective modifying the noun 'prato' to indicate its origin.
Ela aprendeu a cozinhar um prato típico russo.
She learned to cook a typical Russian dish.
In this example, 'russo' is a noun representing the Russian language.