Grammar

Verbs and the accusative (indefinite articles)

Most German sentences contain at least one conjugated verb and a component in the nominative that it modifies - a subject. 

Many verbs, however, also require other components in the nominative - or components in the accusative, dative or genitive (objects). Direct objects (accusative) are the most common.

Nominative component           for instance with the verb "sein"
Accusative component   for instance with the verbs "haben", "möchten", "rauchen", "trinken"
Dative component   for instance with the verb "zuhören"
Genitive component   extremely rare

 

If the subject or object is a noun, you usually need an article for the singular. If you use an indefinite article, only the masculine form changes in the accusative.
The other forms stay the same. The noun itself doesn't change in the accusative.

       Masculine      Feminine      Neuter
Nominative   ein   eine   ein
Accusative   einen   eine   ein

 

        Verb + nominative       Verb + accusative
Masculine   Das ist ein Stadtplan.   Ich brauche einen Stadtplan.
Feminine   Das ist eine Zeitung.   Ich brauche eine Zeitung.
Neuter   Das ist ein Auto.   Ich brauche ein Auto.
Plural   Das sind Autos.   Ich brauche Autos.

 

Never leave a verb all alone!

Always learn verbs along with the case required by the components they modify!