This is the 779th most frequent Russian word.
вчера
"Вчера" means "yesterday."
Usage indicates a completed action that took place the previous day.
Вчера я посетил музей.
Yesterday, I visited the museum.
Usage asks about events that occurred the day before today.
Ты помнишь, что мы делали вчера?
Do you remember what we did yesterday?
Usage describes the weather, referring to the previous day.