noun
period
PEER-ee-uhd/ˈpɪriəd/
A distinct interval or division of time.
The hourglass measures a short period of time.

Etymology
The pieces express “a going around,” originally a circuit or cycle. A repeated cycle of events came to mean the interval it occupied, leading to the broader sense of a length of time.
In context
it is not because it's a literal 24-hour period but a period of one thousand years
More examples
- The museum explores a period of rapid industrial growth.
- We have math during the first period.
- Her period usually lasts about five days.
Forms
period · periods
periodic adjective — Occurring repeatedly at fairly regular intervals.