Kasus: Nominativ und Akkusativ

Nominativ

The subject of a sentence is the person or thing that is "doing" the verb.

ASK: Who or what is doing?
(who or what is singing? Who or what is sleeping?

The subject of a sentence is always in the nominativ case.

Examples:
The dog is sleeping (who is sleeping? the dog,..)
The man is singing (who is singing? the man...)
The woman sees the girl ( who is seeing? the woman...)
Obama is the President ( Obama is the subject AND the president is also nominative because it follows "to be")


Akkusativ

The  direct object receives the action of the verb.

ASK: Who or what is being 'verbed'?
(who or what is being kicked? who or what is being read?)

The direct object of a sentence is always Akkusativ case

Examples:
The woman sees the girl ( Who is being seen? the girl...)
The girl sees the woman (Who is being seen? The woman...)
The man reads the book (what is being read? The book...)
The cow eats the grass (What is being eaten? The grass....)
The grass is eaten by the cow (What is eaten? The grass...)

The woman sees the girl - The woman is the object of this sentence because she is doing the seeing and the girl is the direct object of the sentence because she is being seen by the woman

The cow is eating the grass OR The grass is eaten by the cow - The cow is the subject of the sentence because it is doing the eating (acting) and the grass is the direct object of the sentence because it is being eaten (acted upon).

Articles and Case

	Nominative
	Definite	Indefinite
Masc.	Der Tisch ist braun.	Das ist ein Tisch.
Fem.	Die Lampe ist neu.	Das ist eine Lampe.
Neut.	Das Fenster ist offen.	Das ist ein Fenster.
Plural	Die Bücher sind interessant.	Das sind keine Bücher.

All of the nouns above are in the nominative case because they are
the subjects of the sentences or because they follow the verb “sein.”

	Accusative
	Definite	Indefinite
Masc.	Ich sehe den Tisch.	Ich habe einen Tisch.
Fem.	Ich sehe die Lampe.	Ich habe eine Lampe.
Neut.	Ich sehe das Fenster.	Ich habe ein Fenster.
Plural	Ich sehe die Bücher.	Ich habe keine Bücher.

The nouns above are all in the accusative case because they are direct objects.

In Summary:

Nominative case  (who or what is verbing?) is used: 

- for the subjects of sentences

- after any form of "to be".

Akkusativ case (who or what is being verbed?) is used:

- for direct objects

- after accusative prepositions