The nominative case is used for the subject of the sentence. The accusative case is used for the direct object in a sentence. For example,
"Der Schriftsteller schreibt einen neuen Roman."
The subject of the sentence is <em>Schriftsteller</em>; this noun is used, therefore, in the nominative case. "What is the author writing? - A new novel." The noun <em>Roman</em> is the direct object; that's why it is used in the accusative case.
Another example:
"Der Mann liest den Brief."
<em>Der Mann</em> is the subject (nominative); <em>den Brief</em> is the direct object (accusative).
Cuándo usar nominativo, acusativo, dativo y genitivo. En alemán existen cuatro declinaciones. El Nominativ se utiliza para indicar el sujeto de la frase, aquél que realiza la acción. El Akkusativ se utiliza para indicar el complemento directo, la persona u objeto que recibe la acción del verbo.
