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.