Questions & Answers about Onun gelmesine çok sevindim.
It’s built as:
- gel-: come
- -me: verbal noun (turns the verb into “coming”)
- -si: 3rd person possessive (“his/her/its” coming)
- -ne: dative case “to/for/about,” with a buffer n (because a case suffix comes after a 3rd-person possessive)
So gelmesine ≈ “to/about his/her coming.”
In Turkish, when a verb is turned into a noun (a nominalized clause), its subject appears in the genitive case and the nominalized verb takes a possessive suffix. That structure is called “genitive–possessive.” Hence:
- onun gelmesi = “his/her coming” (genitive subject + possessed verbal noun) Using nominative o here would be ungrammatical.
You can drop it if the referent is clear from context:
- Gelmesine çok sevindim. (I was very happy about his/her coming.) The 3rd person possessive -si already signals “his/her.” Keep onun for clarity or emphasis, especially if multiple third persons are in play.