"His cat is playing with the dog."

Translation: Seine Katze spielt mit dem Hund.

[ttrain8]

Does anyone have any tips for differentiating between the dative and accusative case? It's been giving me some trouble.

[MattEJones]

In this sentence the Dative case is used because the preposition "mit" uses a dative object. Anytime you see the prepositions Aus, Außer, Bei, Mit, Nach, Seit, Von, or Zu, use dative the dative form for the objects of these prepositions.

[ahmed933]

when should i use (seine, seinen ,...)? plz

[Mithrandir]

Maybe it helps if you remember that accusative is related to the English word accuse. If you could replace the verb with acuse it si accusative.
"He paints the door" could also work as "He accuses the door" (don't think about the sense)
In "He plays with the dog" play cannot be replaced with accuse: "He accuses with the dog" is not a correct sentence

[addelar]

Why is DEM and not DEN?

[niceliz]

The dative case is always used after "mit" so "der Hund" is changed to "dem Hund."

[Wilmonde]

Dem is the masculine dative (Hund is masculine); den would imply a plural dative, and there is only one Hund in the sentence.

[Cacacero]

I wrote "Seine Katze spielt gerade mit dem Hund" and got it wrong. Is it really wrong?

[Ahmad-Sakr]

seine Katze mit dem Hund spielen ???