Breakdown of Учитель начал урок за минуту до звонка.
учитель
teacher
урок
lesson
минута
minute
до
before, until
Questions & Answers about Учитель начал урок за минуту до звонка.
Why do we use both за and до to translate 'before' in this sentence?
This is the standard Russian formula for expressing how much time passes before an event. You use за + [time amount] + до + [event]. If you only used до звонка, it would just mean 'before the bell', and you wouldn't have a grammatical way to attach the 'one minute' part.
Why is минуту in the Accusative case, but звонка is in the Genitive?
Each preposition in this time structure dictates its own case. The preposition за requires the Accusative case for the measurement of time (минута becomes минуту). The preposition до always takes the Genitive case for the reference point or event (звонок becomes звонка).
The word for bell is звонок. Why does it change to звонка instead of 'звонока'?
The word звонок has a 'fleeting vowel'. When you add a grammatical ending like the Genitive -а, the last о in the root drops out to make pronunciation smoother. This is very common in masculine nouns ending in -ок or -ец.
Is урок in the Nominative case here?