This question is about Verbals, that is, ‘fiilimsi‘. In Turkish, there are several participles, in other words ‘verbal -noun suffixes’, such as yı. As is the case with English, we mostly make a complex sentence with relative clauses however, we use postfixes which follow the verb. for example okumak means studying bu with suffixes yı It will be used as a noun ,Ben okumayi öğrendim I had learned the reading ,I think you have to google the title 'fiilimsi' which is one of the most important thing in Turkish grammar.