Latin 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 six cases in Latin (more detailed description is below):
nominative – Who did it ? The man did it - case of the subject : Vir (nominative) id fecit, I did it – Ego id feci
accusative – Who(m) do I see ? I see a man – Virum video - case of the direct object, Lucius me videt - Lucius sees me.
dative – to whom ? indirect object case : I give it to Lucius – Lucio id do , I give it to him – ei id do
genitive – whose ? (similar to the Saxon genitive) domus viri – 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 "ab" it's always the dative, after "apud" it's accusative:
ab amicis, apud Romanos
3. Verb government : sometimes it's the verb which decides. Most verbs govern accusative, but there are plenty of exceptions.


Functions of the cases :
1. Nominative is the case of the subject.
The cat sees the dog. Cattus (subject) canem (direct object) videt.
I love him. Ego (subject) eum (direct object) amo.
Both „cattus” and „ego” are in nominative, because they are the subject of the sentence. In Latin, subject pronouns are mostly omitted, so one can say : Eum amo.
2. Accusative is the case of the direct object. In the sentences above, „canem” and „eum” are in the accusative. The forms „me, us, him, her, whom” in English are very often used where the Romans use the accusative.
The accusative is also a case after some prepositions : ad, ante, apud, inter, per, post.
3. Genitive is the case of belonging, similar to the Saxon genitive or to the construction with „of”.
Domus viri – the man's house.
Initium libri – the beginning of the book.
4. Dative is the case of the indirect object.
(Ego) ei librum do – 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”.
5. Ablative is the case standing after many prepositions : a / ab, e / ex , cum, de , pro, sine.
The ablative denotes a tool : gladio occisus – killed with a sword.
In some situations, the ablative can denote time : eodem die it (goes on the same day), eo die castra fecit, ea nocte profiscitur. It can also denote a place : eo loco (in this place), loco citato.
The ablative stands after the preposition in to denote a place : in Italia est. But the accusative is used to denote movement (English into, to) : in Italiam venio.
The vocative is the case of addressing somebody : Marce, veni – Mark, come.