Cases.

There are four cases in German:

- Nominativ (nominative)

- Genitiv

- Dativ (dative)

- Akkusativ (accusative).

German cases.

The cases exist also in English: one is Saxon Genitive, one is the form „me, us, him, her, whom”, different from „I, we, he, she, who”.
There are four cases in German (more detailed description is below):
nominative – Who did it ? The man did it - case of the subject : der Mann (nominative) machte es, I did it – ich machte es
accusative – Who(m) do I see ? I see a man - ich sehe einen Mann- case of the direct object, he sees me – er sieht mich
dative – to whom ? indirect object case : I give it to the man - ich gebe es dem Mann , I give it to him – ich gebe es ihm
genitive – whose ? (similar to the Saxon genitive) das Haus des Mannes – the man's house / the house of the man.
Three things are important in deciding what case to use:
1. Function of the noun in the sentence (subject is in nominative, direct object in accusative, indirect object in dative)
2. After prepositions: the preposition decides, for example after "von" it's always the dative, after "durch" it's accusative:
von dem Mann, von dem Haus
3. Verb government : sometimes it's the verb which decides, for example : helfen (help), gehören (belong) govern the dative :
ich helfe dem Mann. Most verbs govern accusative (sehen, haben, lieben, machen and so on).

Functions of the cases :

1. Nominative is the case of the subject.
The cat sees the dog. Die Katze (subject) sieht den Hund (direct object).
I love him. Ich (subject) liebe ihn (direct object).
Both „die Katze” and „ich” are in nominative, because they are the subject of the sentence.
2. Accusative is the case of the direct object. In the sentences above, „den Hund” and „ihn” are in the accusative. The forms „me, us, him, her, whom” in English are very often used where the Germans use the accusative.
3. Genitive is the case of belonging, similar to the Saxon genitive or to the construction with „of”.
Das Haus des Mannes – the man's house.
Der Anfang des Buches– the beginning of the book.
4. Dative is the case of the indirect object.
Ich gebe ihm ein Buch – I give him a book / I give a book to him.
Here „ihm” is in the dative. In English, the dative is often translated by the preposition „to”.

How to form the cases :

Akkusativ is different from Nominativ only in the masculine gender :
der Mann, die Frau, das Kind, die Leute : ich sehe den Mann, die Frau, das Kind, die Leute
Der changes into den, ein in masculine – into einen. The general rule is „-en” for adjectives, articles in the masculine, else like nominative.
Dative :
in masculine and neuter gender -m, in feminine gender -r, in plural -n :
der Mann, die Frau, das Kind, die Leute : ich helfe dem Mann, der Frau, dem Kind, den Leuten
ein Mann, eine Frau, ein Kind, Leute : ich helfe einem Mann, einer Frau, einem Kind, Leuten
The plural nouns in -e, -r, -l get additional -n in dative plural.
Rules for the genitive are more complicated : it's -s in masculine and neuter nouns, -r in feminines and in plural. Additionally, there is an ending -(e)s in masculine and neuter nouns.
Personal pronouns have, like in English, special forms : ich, Dativ mir, Akkusativ mich and so on...