Learn Turkish: Elbiseyi nerede denemek istiyorsun? - Where do you want to try on the dress?

We add the -yi ending because it is a specific direct object. We are talking about "the" dress, not just any dress. The -y- is a buffer letter to keep the two vowels from bumping into each other, and the -i is the specific object marker.

Why do we use nerede (where) instead of nereye (where to)?

In Turkish, nerede is used when an action happens in a fixed location (like inside a fitting room). We use nereye only when there is movement or direction toward a place. Since trying on a dress happens in one spot, we use the location marker -de in nerede.

How do you link "want" and "try" together in this sentence?

Just like in English, you use the dictionary form (infinitive) of the action verb and place it before the verb for "want". Here, denemek means "to try" and istiyorsun means "you want". Put together as denemek istiyorsun, it means "you want to try".

Why is the question word nerede placed in the middle of the sentence?

In Turkish, question words usually sit right in front of the verb they are asking about. Since the main verb phrase here is denemek istiyorsun (you want to try), the question word nerede goes right before it. The object elbiseyi goes at the beginning.