A priori probability
of an event
The probability of the event, considered in contrast to the conditional probability of the same event under certain additional conditions. The latter is called the a posteriori probability. This terminology is, as a rule, used in connection with the Bayes formula.
A priori probability. Yu.V. Prokhorov (originator), Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=A_priori_probability&oldid=17745