Return period
From Glossary of Meteorology
return period
(Also called recurrence interval.) The average time until the next occurrence of a defined event.
When the time to the next occurrence has a geometric distribution, the return period is equal to the inverse of probability of the event occurring in the next time period, that is, T = 1/P, where T is the return period, in number of time intervals, and P is the probability of the next event's occurrence in a given time interval.
