Breakdown of В этот момент он был дома.
он
he / it (for a masculine noun) / it (for a neuter noun)
дома
at home
этот
this [f: эта, n: это]
быть
to be
Questions & Answers about В этот момент он был дома.
Why is в этот момент used here instead of во время, which we are learning in this lesson?
Во время translates to "during" and must be followed by an event or period in the Genitive case (for example, во время ужина - during dinner). To say "at this/that moment" or to point to a specific snapshot in time, Russian uses the preposition в plus the Accusative case: в этот момент.
Why is этот момент in the Accusative case rather than the Prepositional case?
When the preposition в is used to pinpoint a specific moment or unit of time (like a minute, an hour, a day, or a moment), it takes the Accusative case. The Prepositional case with в is mostly used for physical locations or much longer periods of time, like months and years.
Why does the translation say "at THAT moment" if этот translates to "this"?
In English narrative, we often shift to "that" when talking about the past. In Russian, в этот момент is a very standard set phrase used for both "at this moment" (present) and "at that moment" (past). While you can occasionally use в тот момент for emphasis, в этот момент is extremely common even when narrating past events.
Is дома in the Genitive case here because of some hidden preposition?
No, there is no hidden preposition here. While it looks exactly like the Genitive singular of дом, дома functions here as a fixed adverb meaning "at home" (showing location). Just remember to keep it separate from домой, which is the adverb used for motion ("going home/homeward").