Merhaba!

I am a native Polish speaker and we distinguish a noun case which is used when we are calling someone (Vocative case). It is similar to Arabic ya يا I think, for example: uhibbuki ya gadda - I love you grandma! Is there some kind of Vocative case existing in Turkish? For example when I want to call "Good morning mum!" how should I say this in Turkish? Günaydın, annem! or Anneye günaydın! , maybe Anneme günaydın! ?

There are officially only five cases in the Turkish language. All the cases are created by unique suffix. These cases are the nominative, accusative (suffix -i), dative (suffix -e), locative (suffix -de), and ablative (suffix -den). As nouns, adjectives and adverbs are not inflected at all, the cases have not the importance that is given to them in some Indo-European languages. The genitive is not considered a case at all, although it is frequently used. The existence of something like the vocative case is oblivious to people, although a case coming from Arabic is used in archaic (often religious) or cynical cases. Examples:

• Ey iman edenler!

  O ye who believe!

• Ey aptal!

  O you stupid!

So, finally, how to call Good morning, mum! or I love you, my friend! ??

As in English:

Günaydın, anne!

Seni severim, arkadaşım!

Sometimes which syllable is stressed has different meanings.

Çocuğum = I am a child

Çocuğum = my child

Çocuğum = hey kid

Thank you all, that really explains

We usually stress the first syllable to get some attention to what we say. That´s also an opportunity for vocative case. That explains why we don´t have a suffix for it and also why separate attention catcher words like "hey" is used less or not preferred.