This is the 68th most frequent Turkish word.
türkiye
"Türkiye" means "Turkey," a country located at the crossroads of Europe and Asia.
Here, 'Türkiye' refers to the country Turkey, acting as the proper noun subject of the sentence.
Türkiye güzel bir ülke.
Turkey is a beautiful country.
In this sentence, 'Türkiye'nin' is the possessive form of 'Türkiye' (Turkey), indicating ownership regarding the capital.
Türkiye'nin başkenti Ankara'dır.
The capital of Turkey is Ankara.
Here, 'Türkiye'de' means 'in Turkey', using a locative suffix '-de' to indicate location.