Bygone means belonging to an earlier time that has passed and won't return. When historians study bygone eras like ancient Rome or medieval Europe, they're examining civilizations that existed long ago. When your grandparents reminisce about bygone days of their childhood, they're remembering a time that's gone forever.

The word carries a sense of something being finished and left behind. A bygone tradition might be something people once did regularly but no longer practice, like writing letters by hand instead of sending texts. Bygone fashions are styles that were popular decades ago but look old-fashioned now.

People often use the phrase “let bygones be bygones” to suggest forgetting old arguments or hurt feelings. If two friends had a fight last year but want to move forward, they might agree to let bygones be bygones, meaning they'll stop dwelling on past conflicts and start fresh.

The word usually feels nostalgic rather than sad. When someone speaks of bygone summers at their family's lake house, they're fondly remembering good times from the past, while accepting that those particular days are over.