This is the 835th most frequent Croatian word.
osobi
"Osobi" means "to the person" or "to a person" in English.
In this sentence, 'osobi' is in the dative case, indicating the indirect object of the action, as it's the recipient of the keys.
Dala sam osobi ključeve od stana.
I gave the keys to the apartment to the person.
Here, 'osobu' is in the accusative case, as it is the direct object of the action 'prepoznala' (recognized).
Prepoznala sam osobu na slici koja se smije.
I recognized the person in the picture who is smiling.
In this example, 'osobom' is in the instrumental case, showing the means through or with which the action 'razgovarao' (spoke) is conducted.