Vowel Harmony In Turkish, vowels within a (native) word and any suffixes that are attached to said word must obey vowel harmony rules. This means that vowels tend to either be the same or similar, making words easier to pronounce than they may look.
There are two types of vowel harmony in Turkish: 4-way and 2-way. The accusative case uses 4-way vowel harmony. In order to figure out what may go on the end, you will have to look at the final vowel in the word.
Turkish Accusative Suffix ö, ü -(y)ü o,u -(y)u e,i -(y)i a,ı -(y)ı If the noun ends in a vowel, you have to insert the buffer letter y. Here are some examples:
elma elmayı apple
gazete gazeteyi newspaper
"Accusative" is one of many grammatical cases in Turkish. It is used to mark specific direct objects.
I am guessing that you speak Arabic :) On the end of some words in Arabic, you can add an optional fatHa to show it is the direct object. That is the accusative case. Remember though, it is not the same in Turkish as Arabic :)
Djordje, in his comment above, AlexiNotTurkey answers to your question:
"Elma yerim has not accusative case marker. This means it must be a general direct object. "I eat apples/an apple." Elmayı yerim has the accusative, which means that it must be a specific direct object. "I eat the apple"." Try to read the comment before asking. That's very helpfull. I always find the answer i need.