Nominative or accusative?
Nominativ oder Akkusativ?
Distinguish the person doing an action from its direct object, especially der → den and ein → einen.
The nominative usually marks who performs the action. The accusative marks the direct object. For masculine nouns, der changes to den and ein changes to einen.
Der Mann kauft einen Kaffee.
The man buys a coffee.
Ich sehe den Bus.
I see the bus.
Wir brauchen einen Scanner.
We need a scanner.
Die Frau nimmt die Tasche.
The woman takes the bag.
Ich habe das Ticket.
I have the ticket.
Er sucht einen Arzt.
He is looking for a doctor.
In Der Mann kauft einen Kaffee, Der Mann is the subject and einen Kaffee is the object. Feminine die and neuter das look the same in nominative and accusative at this level.
Use the accusative when buying, seeing, needing, taking, having, or looking for something or someone.
Kaffee is masculine. As the object of kauft, say einen Kaffee, not ein Kaffee.
Masculine object: der → den; ein → einen. First find who acts, then what receives the action.
Identify the subject and object in all six phrases, then replace one object with another masculine noun.