This is the 836th most frequent Croatian word.
osobu
"Osobu" means "person" in English (accusative form).
In this sentence, 'osobu' is used in the accusative case, referring to 'a person' as the direct object of the action 'saw'.
Vidjela sam jednu osobu kako ulazi u park.
I saw a person entering the park.
Here, 'osoba' is in the nominative case and denotes 'a person' required for completing a task.
Treba nam odgovorna osoba za ovaj zadatak.
We need a responsible person for this task.
In this case, 'osobom' is in the instrumental case, used to indicate interaction or communication with 'the person'.