This is the 17003rd most frequent Turkish word.
çantasını
"Her/his/its bag."
The word 'çantasını' is used possessively to indicate 'Mehmet's bag' and operates as the direct object in the sentence, receiving the action of placement.
Mehmet çantasını masanın üstüne koydu.
Mehmet put his bag on the table.
The word 'çantasını' signifies Ayşe's possession of the bag and functions as the direct object being checked.
Ayşe çantasını kontrol etti.
Ayşe checked her bag.
The word 'çantasını' here is used to indicate possession while also functioning as the object of the verb 'lose' in the context of caution.