The Accusative Case: the object and the destination
Кого́? Что? — the thing acted on, the place you are going to after в and на, and the time or duration something takes.
The Accusative's first job is the direct object: Я чита́ю кни́гу, Она́ лю́бит му́зыку, Мы покупа́ем хлеб. Because Russian has no articles, the ending is the only thing telling you which noun is being acted on. The endings are: feminine -а/-я becomes -у/-ю (кни́га → кни́гу, семья́ → семью́); masculine inanimate and neuter look exactly like the Nominative (стол → стол, окно́ → окно́); masculine animate looks exactly like the Genitive (брат → бра́та, студе́нт → студе́нта); the plural is the Nominative shape for inanimates and the Genitive shape for animates. That last rule is animacy, and it has its own entry.
Its second job is direction. With в and на the Accusative answers куда́? — where to? Я е́ду в Москву́, Мы идём на рабо́ту, Он идёт в шко́лу, Де́ти бегу́т на у́лицу, Она́ е́дет на юг. Set this against the Prepositional, which answers где? — where? Я живу́ в Москве́, Она́ рабо́тает на по́чте. Same preposition, different ending, different question. Where am I — Prepositional; where am I going — Accusative. This single pair is the most drilled contrast in the whole case spine, and once it is automatic, half the difficulty of Russian disappears.
Its third job is time and duration. Duration takes the bare Accusative with no preposition at all: Я рабо́тал всю неде́лю, Он ждал це́лый день, Мы говори́ли два часа́. A specific point in time takes в plus the Accusative: в понеде́льник, в суббо́ту, в три часа́, в пе́рвый раз, в э́ту среду́. The word год is the exception and takes the Prepositional instead: в э́том году́, в про́шлом году́. For repetition Russian prefers по plus the Dative plural: по суббо́там, по вечера́м.
A fourth use is worth recognising because it appears in the very first phrase you learn. In some fixed sentences the person is in the Accusative even though English makes them the subject: Как вас зову́т? — literally 'how do they call you'; Меня́ зову́т А́нна; Его́ зову́т Бори́с. There is no grammatical subject in that sentence at all. The prepositions that govern the Accusative are в, на, за, под, че́рез and про; the full map is under prepositions-map.
Examples
- Я чита́ю кни́гу. I am reading a book. Listen in Russian: Slow in Russian: Я чита́ю кни́гу.
- Она́ лю́бит му́зыку и теа́тр. She loves music and the theatre. Listen in Russian: Slow in Russian: Она́ лю́бит му́зыку и теа́тр.
- Мы е́дем в Москву́. We are travelling to Moscow. — куда́?, so the Accusative Listen in Russian: Slow in Russian: Мы е́дем в Москву́.
- Я живу́ в Москве́. I live in Moscow. — где?, so the Prepositional Listen in Russian: Slow in Russian: Я живу́ в Москве́.
- Как вас зову́т? — Меня́ зову́т А́нна. What is your name? — Anna. (literally: how do they call you) Listen in Russian: Slow in Russian: Как вас зову́т? — Меня́ зову́т А́нна.
- Он рабо́тал всю неде́лю. He worked all week. — duration takes the bare Accusative Listen in Russian: Slow in Russian: Он рабо́тал всю неде́лю.