Breakdown of Мама накрыла торт салфеткой.
торт
the cake
мама
the mother
салфетка
the napkin
накрыть
to cover
Questions & Answers about Мама накрыла торт салфеткой.
Why is салфеткой in that form instead of салфетка?
Because салфеткой is in the instrumental case.
In this sentence, the napkin is the thing used to cover the cake, so Russian marks it with the instrumental:
- салфетка = napkin (dictionary form, nominative)
- салфеткой = with a napkin / by means of a napkin
Russian often uses the instrumental case without a preposition where English uses with.
So:
- Мама накрыла торт салфеткой. = Mom covered the cake with a napkin.
For a feminine noun like салфетка, the instrumental singular ending here is -ой:
- салфетка → салфеткой
Why is торт unchanged? Shouldn’t it have a special object ending?
Торт is the direct object, so it is in the accusative case. But for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.
So:
- торт = nominative
- торт = accusative
That is why you do not see a change.
Compare:
- Я вижу торт. = I see a cake.
- На столе торт. = There is a cake on the table.
Same form, different case function.