The sidereal periods of the planets vary greatly.

Employees are required to give two months' notice periods before resigning.

During question periods, the members of parliament can ask the government ministers about various issues.

During the school day, students have several free periods to study or relax.

Elephants have long gestation periods.

During their honeymoon periods, the newlyweds traveled to different countries.

The company offers generous grace periods for late payments.

The incubation periods for different diseases can vary greatly.

I have been experiencing heavy menstruation periods lately.

Periodic sentences are often used in persuasive writing.