Learn Turkish: Çalıştığın tiyatroda prömiyer başladığında çok heyecanlıydık. - When the premiere started at the theater where you work, we were very excited.

This word uses the grammar structure taught in this lesson: the verb root başla (to start) + -dık (makes it a noun-like clause) + -ı (third-person possessive, 'its') + -nda (locative case, 'at/in'). Literally, it means 'at the time of its starting'. Because the subject of the starting is prömiyer, we use the third-person possessive -ı. Notice how the k in -dık changes to a soft ğ before the vowel.

I see a form of the -dık suffix in both çalıştığın and başladığında. Are they doing the same thing?

They are related but do different jobs here! In çalıştığın (the one you work at), the suffix creates a relative clause acting as an adjective for tiyatro. In başladığında (when it started), it creates a time clause that takes the locative suffix -nda to show exactly when something happened. Both use possessive endings to show who does the action: -ın (your) for working, and -ı (its) for starting.

Why doesn't başladığında have a 'we' suffix if the sentence ends with 'we were excited'?

The 'when' clause has its own independent subject: the premiere. Therefore, başla takes the third-person possessive -ı to match the premiere. The main action of the sentence has a different subject ('we'), so heyecanlıydık takes the first-person plural suffix -k.

What suffixes are attached to the adjective to make ?