Der Hund schläft.
English: The dog is sleeping.
The nominative case (Nominativ) in German is used for the subject of a sentence – the person or thing doing the action.
Use the nominative case for the subject of a sentence, and after the verb 'sein' (to be) when describing or identifying someone or something.
Der Hund schläft.
English: The dog is sleeping.
Die Frau liest.
English: The woman is reading.
Das Buch ist interessant.
English: The book is interesting.
Die Kinder spielen.
English: The children are playing.