Learn Turkish: Polis suçluyu trene binerken kıskıvrak yakaladı. - The police caught the criminal firmly while he was getting on the train.

The suffix -(y)ken (while) does not have personal markers, so it usually refers to the subject of the main sentence. However, with verbs of catching, discovering, or perceiving like yakalamak, the -(y)ken clause often modifies the direct object in the accusative case. Because suçluyu is in the accusative, it acts as the subject of the boarding action.

Why is the word for train written as trene instead of treni?

The verb binmek (to board or to get on) always requires the destination to be in the dative case. The dative suffix -e is added to tren, making it trene to show what the criminal is getting onto.

What exactly does kıskıvrak mean in this context?

The word kıskıvrak is a specific adverb meaning firmly, tightly, or without leaving any chance of escape. It is almost exclusively used with a few verbs like yakalamak (to catch) or bağlamak (to tie up) to emphasize that the person was completely subdued.

Would the meaning change if we moved trene binerken to the very beginning of the sentence?

Yes, word order is crucial here. If you put the -(y)ken phrase first, it sounds like the police were the ones boarding the train when they made the arrest. Keeping suçluyu right before the boarding action makes it clear that the criminal is the one getting on the train.