This is the 12800th most frequent Turkish word.
izinlerinin
"İzinlerinin" means "of their permissions" or "their leaves" in English, depending on context.
In this sentence, 'izinlerinin' refers to the leaves or permissions belonging to the employees (possessive form).
Çalışanların izinlerinin düzenlenmesi biraz zaman alıyor.
Organizing the employees' leaves takes some time.
Here, 'izinlerinin' specifies the permissions needed for completing the project (possessive form and origin indicated).
Projeyi tamamlamak için yönetimden izinlerinin alınması gerekiyor.
To complete the project, their permissions must be obtained from the management.
In this usage, 'izinlerinin' denotes the specific leaves (vacations) starting tomorrow belonging to the students (possessive form).