ˌgeneˈration ˌgap noun [singular]
the lack of understanding or the differences between older people and younger people

[TahlilGaran] Dictionary of Contemporary English ▲

generation gap
the lack of understanding between older and younger people that is caused by their different experiences, opinions and behaviour.
It is unusual for a singer to bridge the generation gap and appeal to both young and old alike.

There's a big age difference between us but we've never been troubled by a generation gap.

[TahlilGaran] English Idioms Dictionary ▲

generation gap
n., informal, hackneyed phrase The difference in social values, philosophies, and manners between children and their parents, teachers and relatives which causes a lack of understanding between them and frequently leads to violent confrontations.
My daughter is twenty and I am forty, but we have no generation gap in our family.

[TahlilGaran] English Idioms Dictionary ▲