I presume you want to know what it is in English. Other languages have different ways to indicate it but in English it is indicated in English often by -'s or of. It is often called the possessive case because it shows possession...ex John's car is old. This means The car of John is old (Spanish always says it this way: El carro de John is viecho ) English also uses "of" but differently: a bottle of wine. Here the genitive case is a way to describe what is particular about the bottle ( not a bottle of mil, not a bottle of juice etc.) Hope this helps, John

Genitive case is a part of Latin grammar which has, idiotically, been assumed to also exist as perfectly in English. Ignore it. Genitive case only makes sense if the form of the noun actually changes frequently. This does not happen in English. I've discussed this issue with teachers of languages which DO have genitive case, and it simply doesn't fit in English grammar. "Possessive" exists, but it's not the same as genitive.

It is the possessive. Usually indicated by the preposition "of", or the apostrophe-s. http://en.wikipedia.org/wiki/Genitive_case