

Однажды я опоздал на поезд.
Once I missed the train.
Мы однажды встретились в парке.
We once met in the park.
Однажды мама забыла ключи дома.
Once Mom forgot her keys at home.
"однажды" is in the lesson "Time 3" (Level 40), along with 13 other useful words. LinDuo has 180 topic lessons like this one, 2,380 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.