Learn Turkish: Mühendis altyapının dayanıksız olduğunu gördü. - The engineer saw that the infrastructure was weak.

Since dayanıksız is an adjective, it cannot take the -dık clause endings directly. To create a factive clause with an adjective or noun, Turkish uses the helper verb olmak (to be). The sentence literally constructs the phrase as 'its being weak'.

Why does altyapı take the genitive ending to become altyapının?

In Turkish factive clauses, the subject of the embedded clause acts like a possessor. Because the sentence functions grammatically as 'the infrastructure's being weak', altyapı gets the genitive case -(n)ın, which pairs with the 3rd person possessive suffix -u on olduk.

What are the specific suffixes attached to olduk to make olduğunu?

It breaks down as olduk + -u (3rd person possessive, matching the infrastructure) + -n- (buffer letter) + -u (accusative case). The accusative case is required because the entire phrase altyapının dayanıksız olduğunu is the direct object of the verb gördü. The engineer saw it.

How is the adjective dayanıksız constructed?