Quick answer
A Russian noun changes its ending to show its job in the sentence. Six cases, each with its own question words.
What each case does
| Case | Question | Job | Example |
|---|---|---|---|
| nominative | кто? что? | the subject | Э́то кни́га. |
| genitive | кого́? чего́? | of, none, quantity | нет кни́ги |
| dative | кому́? чему́? | to, for; the experiencer | дать кни́гу дру́гу |
| accusative | кого́? что? | the object; where to | чита́ю кни́гу |
| instrumental | кем? чем? | with, by means of | с кни́гой |
| prepositional | о ком? о чём? | in, on, about | в кни́ге |
The question words are the fastest way in: if you can answer кому́? you have found a dative, and if чем? then an instrumental.
The order to learn them
Textbooks go 1–6. Usefulness goes differently. Start with the nominative and accusative — subject and object, the backbone of any sentence. Then the prepositional, because в Москве́ comes up on day one. Then the genitive, which is the busiest case in the language. The dative next, for мне and нра́вится. The instrumental last — it is the most regular of all.
The good news
Three things make this smaller than it looks. The accusative is identical to the nominative for most inanimate nouns, so half the work is already done. The instrumental has almost no exceptions. And prepositions come welded to their cases — learn в + prepositional and с + instrumental as pairs and you never choose again.
Learn in phrases, not tables
Nobody becomes fluent by reciting six endings. What works is storing whole phrases — в Москве́, с дру́гом, нет вре́мени, мне нра́вится — and letting the pattern assemble itself from examples you actually use.
Typical mistakes
Learning all six at once
Nominative and accusative first
You can build real sentences with two cases; six at once produces paralysis.
Я в Москва́.
Я в Москве́.
в for location takes the prepositional.
Check yourself
Which case answers кому́?