This is the 940th most frequent Polish word.
osobę
The word "osobę" in Polish means "person" (accusative singular form).
Here, 'osobę' is used in its accusative form as it is the direct object of the verb 'widziałem' (I saw).
Widziałem jedną osobę na przystanku autobusowym.
I saw one person at the bus stop.
In this case, 'osobę' is used as the accusative case of the word 'osoba', which means 'person', to indicate the direct object of the verb 'zatrudniłem' (I hired).
Zatrudniłem nową osobę w naszej firmie.
I hired a new person at our company.
'Osobę' is used in the accusative case, as it is the object of the preposition 'o', in the phrase 'pytam o tę osobę' (asking about this person).