These three words have (for me) almost the same meaning when I look at them in the dictionary here on this site.

Nerede: Where?/Where...?/Wherever?

Nereden: Where ...?/From where ...?/Whence?

Nereye: Where?/Where...?/Whither ...?/Wherever?

Anyone who can explain - with examples please - what the difference is? BTW, I´ve never heard anyone say ´´whither´ or ´whence´.... (but that´s probably my shortcoming..   )

Nerede: where

Nereden: where from

Nereye: where to

Neredesin? - Where are you?

Nereden geldin? - where did you come from? (gelmek = to come)

Nereye gidiyorsun? - Where are you going? (gitmek = to go) 

Teşsekkürler, Chantal, but then why in the dictionary all these other possibilities? They confuse me!

I don´t like the dictionary of this website much, it often doesn´t give enough information or is very confusing.. for now I can´t give you a good alternative because I don´t use a digital dictionary..

"nerede" => "at/in where?"

"nereden" => "from where?"

"nereye" => "to where?"

for example:

"Arabam nerede" = "Where is my car?"

"Nereden geliyorsun" = "Where are you coming from?"

"Nereye gidiyorsun" = "Where are you going (to)?"