Forming Relative Clause

Köpek  eti  yedi.  ---> Subject is "Köpek "

The dog ate the meat.

Eti  yiyen  köpek ----> Head of Noun compound is " köpek ", Relative morpheme - En

The dog who ate the meat

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Köpek eti yedi. ---> Object is "et"

The dog at the meat

Köpeğin yediği et  ---> Head of noun compound is "et" ,  Relative morpheme -Dık

The meat whıch the dog has eaten.

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 * When the subject of the sentence becomes the head of Noun Compound, -EN is used.

* Elsewhere , -dIk is used.

Arkadaşım Türkçe biliyor. ---> Subject is " Arkadaşım "

Subject becomes the head of noun compound ---->

Türkçeyi bilen arkadaşım.

                    the head of NC

Arkadaşım Türkçe  biliyor. ---> Object  is  "Türkçe"

Object becomes head of noun compound ----->

Arkadaşımın  bildiği  Türkçe

                           head of Noun compound

The Turkish that my friend knows

Therefore,  Relative morpheme -dIk is used.