This is the 59th most frequent Ukrainian word.
росія
"Росія" translates to "Russia," the name of a country.
Here, 'Росія' functions as a proper noun referring to the country Russia in a geographical and factual context.
Росія є найбільшою країною у світі.
Russia is the largest country in the world.
In this sentence, 'Росії' represents the genitive case of the noun 'Росія', indicating possession towards 'історія' meaning 'history'.
Історія Росії містить багато важливих подій.
The history of Russia contains many important events.
Here, 'Росією' is in the instrumental case of the noun 'Росія', indicating an entity with which actions are related.