Olympiad mind-sports, such as the Science Olympiad, Mindsport Olympiad, Chess Olympiad, International History Olympiad and Computer Olympiad. In these cases "Olympiad" is used to indicate a regular event of international competition for top achieving participants; it does not necessarily indicate a four-year period. In some languages, like Czech and Slovak, Olympiad () is the correct term for the games. "The Olympiad" ("L'Olimpiade") is also the name of some 60 operas set in Ancient Greece. Olympiad An Olympiad (, "Olympiás") is a period of four years associated with the Olympic Games of the Ancient Greeks. During the Hellenistic period, beginning with Ephorus,
Return period interest and formula_5 is the counting rate. If the return period of occurrence is 1 in 234 years (formula_5 = 0.0043) then the probability of no occurrence in ten years is In a given period of "n" years, the probability of a given number "r" of events of a return period formula_5 is given by the binomial distribution as follows. In the limit of :formula_11, such that formula_12 then Take where Given that the return period of an event is 100 years, So the probability that such an event occurs "exactly once" in 10 successive years is: Return period is