Nouns, Articles, and Case Endings
Case is determined by function, not form
In the Greek language, it is important to understand that the relationship of the noun to the other words in the sentence always governs the case. Hence, although Genitive and Ablative share the same endings, they are clearly distinguished within the context and function of the sentence. There are eight cases in the Greek language: Nominative, Genitive, Ablative, Dative, Locative, Instrumental, Accusative, and Vocative.
The case of direct address.
The case of specific designation, the naming case.
The case of definition or description.
The case of personal interest. It expresses the indirect object.
The case of position or location.
The case of means or association.
The case of limitation or extension.