Learn Turkish: Yeni stadyum açık olsaydı, finali orada oynardık. - If the new stadium had been open, we would have played the final there.

It comes from the verb olmak (to be/become). We add the conditional suffix -sa (if) and the past tense suffix -ydı (was/were). Together, ol-sa-ydı creates the past counterfactual meaning 'if it had been'. When paired with the adjective açık (open), açık olsaydı means 'if it had been open'.

Why does oynardık mean 'we would have played'? Doesn't the aorist past usually mean 'we used to play'?

Yes! Outside of 'if' sentences, oynardık (built from the root oyna-, the aorist -r, the past -dı, and the 'we' ending -k) often means 'we used to play' as a past habit. However, in Type 3 conditional sentences like this one, the aorist past is the standard way to express what you 'would have done' in the result clause.

Could we attach the conditional suffixes directly to açık and say açıksaydı instead of using olsaydı?

You can, but there's a slight difference in feel. açıksaydı usually implies 'if it was open' (maybe it was, maybe it wasn't, we just didn't know). Using the helper verb in açık olsaydı makes it a clear Type 3 counterfactual: we know the stadium wasn't open, but we are imagining 'if it had been open'.

Why is there an -i at the end of finali?