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.