Learn Turkish: Olay üzerine polis, toplatılan ürünlere geldikleri gün el koydu. - Upon the incident, the police confiscated the recalled products on the day they arrived.

In this lesson's context, üzerine following a noun means upon or immediately following and in response to. So olay üzerine means upon the incident. It shows a sequence of events where the incident directly triggered the police's reaction, rather than meaning on top of in a physical sense.

Why is the dative case used in ürünlere?

The verb phrase el koymak means to confiscate or to seize (literally to put hand to). In Turkish, you put a hand to something, so this verb always requires the dative case. Therefore, confiscated the products becomes ürünlere el koydu.

How does the word toplatılan break down to mean recalled?

It is a chain of suffixes built on toplamak (to gather or collect). Adding the causative suffix gives toplatmak (to have someone gather, which is the standard term for recalling a product). Then the passive suffix makes it toplatılmak (to be recalled). Finally, the subject participle -an turns it into the adjective toplatılan (which were recalled).

Why is it geldikleri gün for the day they arrived?