This is the 4770th most frequent Turkish word.
doktorun
"Doktorun" means "the doctor's" (possessive form).
Here, 'doktorun' is the possessive form of 'doktor' (doctor), indicating ownership of the room.
Doktorun odasında birkaç ilaç vardı.
There were some medicines in the doctor's room.
In this sentence, 'doktorun' is the genitive form, indicating whose side or whom to go to.
Bugün hastanede doktorun yanına gitmen gerekiyor.
You need to go to the doctor at the hospital today.
Here, 'doktorun' implies genitive case, expressing 'what of the doctor' or 'what the doctor said.'