曾 (céng): однажды

I once lived in Shanghai for three years, and that experience taught me a lot.

She once said she would come to my birthday party, but in the end she couldn't make it because she was too busy with work.

This scientist once won a Nobel Prize, and his research changed our understanding of the universe.

When I was little, I once had a puppy; it would wait for me at the door every day after school.

He once worked at that company for five years, but later quit to pursue his dream.

We once agreed to go see the sea together, but we had to cancel the plan because of the weather.