Answer:
period.
Step-by-step explanation:
Periods can be defined as the amount of time required for one complete cycle to occur.
For example, the menstrual cycle in women, even though it varies in ladies, it is an example of a period. its is simply the length of time from the day of the menstrual cycle to the day before her next period. so its a cycle which requires counting days, and that is why we say the amount of time required for one cycle to occur is called the period