The six cases: what the system is actually for
Six cases, six questions, and endings that do the work English needs word order for and Italian needs articles and prepositions for.
Russian has six cases. Имени́тельный (Nominative) is the subject and answers кто? что?. Роди́тельный (Genitive) answers кого́? чего́? and covers absence, possession, quantity and origin. Да́тельный (Dative) answers кому́? чему́? and covers the person something is aimed at. Вини́тельный (Accusative) answers кого́? что? and covers the direct object, the destination and duration. Твори́тельный (Instrumental) answers кем? чем? and covers means, company and role. Предло́жный (Prepositional) answers о ком? о чём? and, with в and на, covers location. Learn the six questions and you have learned the shape of the whole system.
What the system replaces is the important part for an English speaker. Russian has no articles, so a good deal of the work that the and a do in English — and that definite articles do in Italian — is carried instead by word order, by intonation and by the case ending itself. The ending tells you whether a noun is the doer, the receiver, the place or the tool, which in English needs a fixed word order plus prepositions. It also removes a great many prepositions outright: кни́га бра́та needs no 'of', писа́ть ру́чкой needs no 'with', я ду́маю о рабо́те is the one place where Russian keeps a preposition that English drops.
The scale, stated honestly. There are three main declension classes plus the irregulars, and each noun has twelve forms — six cases in two numbers. Adjectives, demonstratives and possessives agree and decline in parallel, so a noun phrase like о большо́й но́вой кни́ге contains three words each carrying the same case information. That sounds like a great deal, and it is why Russian is taught one case at a time rather than all at once. The saving grace is that endings are shared across classes: the Dative plural of every noun of every gender is -ам or -ям, the Instrumental plural is -ами or -ями, the Prepositional plural is -ах or -ях. You are learning patterns, not a thousand separate words.
The order this course uses — Nominative, Prepositional, Accusative, Genitive, Dative, Instrumental — is the standard Russian-as-a-foreign-language sequence, chosen for frequency, regularity and immediate usefulness rather than for the order grammar books traditionally print them in. By the end of Lesson 12 all six are on the table and the entire map fits on a single page. When you meet a form you cannot identify, use the case-questions diagnostic; when a preposition confuses you, go to the prepositions-map.
Examples
- Студе́нт чита́ет кни́гу. The student is reading a book. — Nominative subject, Accusative object Listen in Russian: Slow in Russian: Студе́нт чита́ет кни́гу.
- Кни́га студе́нта лежи́т на столе́. The student's book is lying on the table. — Genitive for possession, Prepositional for place Listen in Russian: Slow in Russian: Кни́га студе́нта лежи́т на столе́.
- Я дал кни́гу студе́нту. I gave the book to the student. — Dative for the recipient Listen in Russian: Slow in Russian: Я дал кни́гу студе́нту.
- Студе́нт пи́шет ру́чкой вме́сте с дру́гом. The student is writing with a pen, together with a friend. — Instrumental for both Listen in Russian: Slow in Russian: Студе́нт пи́шет ру́чкой вме́сте с дру́гом.
- Мы говори́ли о студе́нте. We talked about the student. — Prepositional for the topic Listen in Russian: Slow in Russian: Мы говори́ли о студе́нте.
- Я иду́ к студе́нту. I am going to the student's. — Dative with к for movement towards Listen in Russian: Slow in Russian: Я иду́ к студе́нту.