Originally posted by: TseDanylo on Duolingo Archived here
Вітаю!
Ukrainian is an East Slavic language spoken primarily in Western and Central Ukraine by 40 million people making it the third most spoken Slavic language by number of native speakers in the world!
If there are any terms you do not understand please refer to the grammar glossary
What is a case?
A case is a suffix or ending added to a word to show its relationship to the other parts of a sentence. In other words, it tells us what the noun's job in the sentence is. Is it doing the action? Receiving it? Is it in/at a place? In Ukrainian, instead of relying on context and prepositions like in English, we add endings onto the word. English has only two cases for nouns (Nominative and Genitive) and two for pronouns (Nominative and Objective). The genitive case in English is a good way of explaining how this works. The genitive case is used to show ownership over and object, in English it's represented by 's or ' for example: The cat -> The cat's, James -> James'. For pronouns: I -> me, he -> him, she -> her. Hopefully this might help you understand roughly what cases are used for. In Ukrainian, the cases are much more complicated but don't worry! You don't need to learn all the cases now, just try one at a time 
How are cases used in Ukrainian?
In Ukrainian, cases are used for a variety of uses. This depends on everything from the subject to the location. In Ukrainian, there are seven cases and one you've been using since you first began the course and another two are very easy and another is used in English so really, they shouldn't be too much of a problem. Here is a conversation between a mother and daughter using all the cases of кіт, meaning cat.
Where is my cat? - Де мій кіт?
I gave the cat to Mariya - Я дала марії кота.
Now you don't own the cat - Ти зараз не має кота.
But I loved to eat with my cat - Але, я любила з'їсти з моїм котом.
And I loved to give the cat sandwiches - Та я любила давати канапки котові.
That's why there was always cheese on your cat - Це тому завжди був сир на твоїм коті.
Oh cat! Where are you now? - Коте! Де ти зараз?
So as we can see, the nouns do change a lot in Ukrainian.
So what are the cases?
I'm gonna add links in the near future to pages dedicated to each case, but for now there will only be a brief description.
- The Nominative Case (Називний Відмінок)
This case is used for the subject or the do-erof the verb or action. For example, in the sentence I eat the apple, I is the subject because it is doing the action of eating. This is also the base form of the noun and is the form found in dictionaries.
- The Genitive Case (Родовий Відмінок)
This case is used to show a nouns ownership over another noun similar to the English cat VS. cat's.
- The Dative Case (Давальний Відмінок)
The dative case is used to mark the indirect object of a sentence. This is a bit difficult for learners and many often confuse it with the Accusative case. The way to think of it is like dominoes, it's not directly affected by the action but instead it's indirectly affected. Hence, the name indirect object For example, in the sentence I give the man the apple, the man is the indirect object since the apple is receiving the action and that's affecting the man. I'll explain this further in a future post.
- The Accusative Case (Знахідний Відмінок)
The accusative case is used to mark the direct object of a sentence. This is the easiest case to form, unlike the dative case it marks the direct object. In other words, the object directly affected/receiving the action. So in the sentence I give the man the apple, the apple is the direct object because it's receiving the action of being given. This will also be further explained in a future post.
- The Instrumental Case (Орудний Відмінок)
The instrumental case roughly translates "with" and "by means of" in English, it better to explain with explain with examples. The words in bold would be in the instrumental case;
- I am eating breakfast with my sister
- I go to school in the car
- I go to work by bus
- The Locative Case (Місцевий Відмінок)
The locative case is another very easy case to form with only one ending and a few peculiarities. This case is used to show location so for example in the sentence, I am at school, school would be in the locative since the in would tell that school is the location.
- The Vocative Case (Кличний Відмінок)
The vocative case is used to directly address someone or something. The English phrase O Lord!, would use the Accusative case or if you were saying something like "Viktor, why are you licking the chair?", Viktor would be in the Vocative case.