This is the 308th most frequent Turkish word.
onu
"Him," "her," "it," or "that" (accusative case).
As a pronoun, 'onu' serves as the object, replacing a third-person pronoun.
Onu yarın okula götürüyoruz.
We are taking her/him to school tomorrow.
'Onu' is a direct object pronoun indicating the person seen.
Resimde onu gördüm.
I saw him/her in the picture.
Here, 'onu' refers to the book as the object affected by the action.