Learn Turkish: Başarı oranının yıldan yıla gerileyeceğini sanmıyoruz. - We do not think that the success rate will regress from year to year.

Yıldan yıla translates to "from year to year" and is built using the pattern Noun + Ablative (-dan) + same Noun + Dative (-a). It acts as an adverb showing gradual progression over time. You can easily apply this to other time words, such as günden güne (day by day) or aydan aya (month by month).

Why is 'başarı oranı' (success rate) in the genitive case here as 'oranının'?

It acts as the subject of the embedded clause "that the success rate will regress." In Turkish, when an entire clause becomes the object of a main verb like sanmıyoruz, the subject of that embedded clause takes the genitive case (oranının), and its verb turns into a participle with a matching possessive suffix (gerileyeceğ-i).

Can you break down all the suffixes on the word 'gerileyeceğini'?

Certainly! The root is gerile- (to regress/decline). Next is the future participle -(y)ecek (which softens to -yeceğ- because a vowel follows). Then we add the 3rd-person possessive -i (which pairs with the genitive oranının). Finally, we have the buffer -n- and the accusative case -i, because this entire embedded clause is the direct object of the verb sanmıyoruz.

Could we use 'düşünmüyoruz' instead of 'sanmıyoruz' at the end of the sentence?