This is the 838th most frequent Hungarian word.
nyíregyházán
"Nyíregyházán" means "in Nyíregyháza," referring to being located in or at the city of Nyíregyháza in Hungary.
Here, 'Nyíregyházán' is used as the inessive case (location).
Nyíregyházán sok érdekes múzeum található.
In Nyíregyháza, there are many interesting museums.
In this sentence, 'Nyíregyházán' is also employed in the inessive case, indicating where the action took place.
Múlt hónapban Nyíregyházán jártam.
Last month, I visited Nyíregyháza.
Here 'Nyíregyházán' demonstrates the place where the speaker grew up, continuing the use of the inessive case.