This is the 626th most frequent Turkish word.
kullandığı
"That he/she/it uses" or "that is used."
In this sentence, 'kullandığı' means 'that he/she used.' It is derived from the verb 'kullanmak' (to use), with a suffix indicating possession and past tense context of use.
Bu, onun projede kullandığı bir yöntemdir.
This is a method he used in the project.
Here, 'kullandığı' translates to 'that he/she drives.' It indicates the vehicle that is being used by the subject, again showing possession and past-present context.
Kullandığı arabanın rengi çok güzel.
The color of the car he drives is very beautiful.
'Kullandığı' refers to the program utilized by the subject, maintaining a similar grammatical function as in the prior examples.