This is the 3437th most frequent Turkish word.
makineleri
"Machines" or "the machines" (plural noun in Turkish, possessive or definite form depending on context).
Here, 'makineleri' is used as the definite plural form of 'makine' (machine), indicating the possession by 'the factory' (fabrikanın).
Fabrikanın makineleri çok eski ve verimsiz.
The machines of the factory are very old and inefficient.
In this sentence, 'makineleri' refers to 'the machines' explicitly mentioning the objects to be checked, showing definite direct object usage.
Makineleri kontrol etmek için biraz zamana ihtiyaç duyuyorlar.
They need some time to check the machines.
'Makineleri' is used as the definite plural direct object in connection with the relative clause 'they repaired', showing specification.