This is the 4921st most frequent Turkish word.
fermuar
Zipper.
Here, 'fermuar' refers to the jacket's zipper mechanism as a noun.
Ceketimin fermuarı bozuldu.
The zipper of my jacket broke.
In this sentence, 'fermuarını' is the possessive form of 'fermuar' used as a direct object.
Fermuarını düzgünce kapattığından emin ol.
Make sure you properly close your zipper.
Here, 'fermuar' is the subject of the action 'to open', showing its functional role.