So, remember how we learned about different types of words like nouns, which are the things we call by their name? Now, when we want to show that there is something missing or that something is not there, we use something called the "abessive case".
Abessive is a fancy word for "not having" or "lacking". When we add the abessive case to a noun, it shows that we're talking about something that doesn't have that noun or is missing that thing.
For example, let's say we have the word "cake". If we add the abessive case to it, it will become "cake-ta" in some languages. This means "without cake" or "not having cake".
It's like if you were having a birthday party and there was no cake. You could say "we are having a party without cake" or "the party is in the abessive case of cake".
So, the abessive case is just a special way of showing when something is not there or is missing.