This is the 973rd most frequent Czech word.
ruským
The Czech word "ruským" means "Russian" (in the instrumental or dative case, singular form).
Here, 'ruským' is used as an adjective to describe the noun 'velvyslancem' (ambassador), indicating their nationality.
Mluvil jsem s ruským velvyslancem.
I spoke with the Russian ambassador.
In this sentence, 'ruským' is describing 'uměním' (art), showcasing the cultural aspect of the adjective.
Byli jsme fascinováni ruským uměním.
We were fascinated by Russian art.
Here, 'ruským' is used attributively to describe the 'vlivem' (influence), linking it back to its origin, Russia.