This is the 15808th most frequent Turkish word.
traktörü
"The tractor" (in the accusative case).
In this sentence, 'traktörü' is used as the direct object of the verb 'kullanmaya başladı' (started using), indicating the item being acted upon.
Ali yeni aldığı traktörü tarlada kullanmaya başladı.
Ali started using the tractor he bought in the field.
Here, 'traktörü' is used as the direct object of the verb 'görmemiştim' (I hadn't seen), referring to the tractor as an item of observation.
Traktörü görmemiştim bu kadar büyük olacağını düşünmüştüm.
I hadn't seen the tractor, I thought it would be this big.
In this case, 'traktörü' is the direct object of the verb 'yıkadıktan' (after washing), specifying the item of action.