Accusative Case in German

Please note, while learning a new language like German, it is best to not translate everything. Understanding the grammar, its rules, and the context of what we want to say and how we say it is very important. However, considering this is a textual medium, I may provide some translations to English for better understanding.

Only the der / masculine article changes to den for accusative case. Rest of the articles remain the same.

bestimmt	Maskulin	Feminin	Neutrum	Plural
	der Mann	die Frau	das Baby	die Kinder
Nominativ	der Mann	die Frau	das Baby	die Kinder
Akkusativ	den Mann	die Frau	das Baby	die Kinder

unbestimmt	Maskulin	Feminin	Neutrum	Plural
	der Mann	die Frau	das Baby	die Kinder
Nominativ	ein Mann	eine Frau	ein Baby	-
Akkusativ	einen Mann	eine Frau	ein Baby	Kinder

Negation	Maskulin	Feminin	Neutrum	Plural
Genus	der Mann	die Frau	das Baby	die Kinder
Nominativ	kein Mann	keine Frau	kein Baby	keine Kinder
Akkusativ	keinen Mann	keine Frau	kein Baby	keine Kinder

I find Akkusativ to be the most simplest to understand.

We'll take some examples here:

Subjekt / Nominativ	Verb	Objekt / Akkusativ	Noun
Ich	kaufe	den Kuchen.	der Kuchen (M)
Du	trinkst	den Kaffee.	der Kaffee (M)
Sie	trinkt	keinen Wein.	der Wein (M)
Ich	kaufe	die Kekse.	der Keks (M)
Er	habt	das Bier.	das Bier (N)
Ich	brauche	die Banane.	die Banane (F)
Wer?		Was?	only for reference

In German, verbs always go in the 2nd position of the sentence.

As a rule of thumb, what you can do is ask the question Wer? or Was? (who or what, respectively).

Wer kauft Kuchen? - to which we get the answer der Kuchen. Hence, we write den Kuchen.

Wer habt Bier? - to which we get the answer Er. Hence, we write das Bier?

Was brauchst du? - to which we get the answer der Kaffee. Hence, we write den Kaffee.

As long as there is a subject in the sentence, the object will be in accusative. There has to be some action done by the subject on the object. When there is an effect brought on by the subject, accusative case will be used.

If we're saying - Der Kuchen ist lecker. The word Kuchen is the subject of the sentence, not the object. There won't be an accusative article here.

Thank you for reading :)