This is the 7261st most frequent Polish word.
juliusz
"Juliusz" is a Polish masculine given name, equivalent to "Julius" in English.
In this sentence, 'Juliusz' is used as a proper noun to name a specific person.
Juliusz mieszka w Warszawie.
Juliusz lives in Warsaw.
Here, 'Juliusza' (genitive case of 'Juliusz') indicates possession, while being part of a proper noun denoting a historic figure.
Czy znasz książki Juliusza Słowackiego?
Do you know the books of Juliusz Słowacki?
In this instance, 'Juliusz' is used as a title or name, potentially metaphorical or symbolic.