rus

In a sentence

• Am cunoscut ieri un profesor rus.

  Yesterday, I met a Russian teacher.

  Here, 'rus' is used as an adjective to describe nationality, indicating the teacher is from Russia.

• Mergem la restaurantul rus din oraș.

  We are going to the Russian restaurant in the city.

  In this context, 'rus' again functions as an adjective, describing the type of cuisine or style associated with Russia.

• Rusul pe care l-am întâlnit a fost foarte prietenos.

  The Russian man I met was very friendly.

  Here, 'rusul' serves as a noun by itself due to the definite article attached to it, referring to a Russian individual (a man).