The accusative case, also the accusative object or direct object, follows certain verbs and prepositions. It is used for the thing or person receiving the direct action of a verb. Because word order is freer in German grammar, we use the accusative case to mark the direct object in a sentence by using different personal pronouns and changing the ending of masculine possessive pronouns. We can use the questions 'wen/was' to find out whom/what is recieving the action of the verb. In a nutshell: The noun as object requires the 4th case (accusative) when the verb requires it (e.g. haben, kaufen, brauchen) or a preposition. When you look up a verb or preposition in the dictionary, you will see which case they require. Here some exercises plus the correct answers (Click the green field for the correct answers: Antworten überprüfen / Lösungen) https://deutsch.lingolia.com/de/grammatik/nomen/deklination/akkusativ/uebungen

Hi, it depends on the verb you use (for example "sehen" is always with Akkusativ: Ich sehe den Vater. --> I see the father.). Some verbs want Akkusativ, it is always an object, not the subject. We have two questions for the Akkusativ: wen? (for persons) and was? (for things). The forms are: maskulin: den, einen, keinen, meinen feminin: die, eine, keine, meine neutrum: das, ein, kein, mein Plural: die, keine, meine For example: Ich (subject) sehe (see) einen Mann, eine Frau, ein Kind und keine Hunde. Other verbs, which want the Akkusativ: lesen, essen, trinken, kaufen (there are a lot of them, for this reason a good tipp is to learn always the verb and the Kasus) :)