forty-year period
noun phraseUK /ˈfɔːti jɪə ˈpɪəriəd/
US /ˈfɔːrti jɪr ˈpɪriəd/
A forty-year period is a stretch of time that lasts forty years.
The old tree grew very tall over a forty-year period.
OTHER MEANINGS
2. A length of time equal to half of a person's eighty-year life.
He worked at the same school for a forty-year period.
3. A way to describe a long era in history or in a project.
The bridge was built during a forty-year period of growth.
4. A fixed amount of time used in planning or studying long changes.
Scientists watched the river change over a forty-year period.