Learn Turkish: Gördüğüm balon çok büyük. - The balloon that I see is very big.

This is the Turkish way of making a relative clause. You take the verb stem gör- (to see), add the participle suffix -dük (a form of -dık), and then add the possessive ending -üm (my). Literally, it translates to "my seen", so gördüğüm balon is "the balloon that I see".

Why does the base suffix -dık change to -düğ- in this word?

Two things happen here. First, vowel harmony changes -dık to -dük to match the rounded vowel in gör-. Second, because the suffix is followed by a vowel (the -üm), the hard k at the end softens into a "soft g" (ğ). So, gör + dük + üm becomes gördüğüm.

Can gördüğüm also mean "that I saw" in the past?

Yes! The -dık participle handles both past and present tenses. Depending on the context, this sentence could perfectly translate to "The balloon that I saw is very big." To specify the future, like "that I will see", you would use the -ecek suffix instead to make göreceğim balon.

How could I use gittikçe in this sentence to say the balloon is getting big?