1. prior probabilityMathematics, See also 事後確率
Wikipedia definition
2. Prior probabilityIn Bayesian statistical inference, a prior probability distribution, often called simply the prior, of an uncertain quantity p (for example, suppose p is the proportion of voters who will vote for the politician named Smith in a future election) is the probability distribution that would express one's uncertainty about p before the "data" (for example, an opinion poll) is taken into account. It is meant to attribute uncertainty rather than randomness to the uncertain quantity.
Read “Prior probability” on English Wikipedia
Read “事前確率” on Japanese Wikipedia
Read “Prior probability” on DBpedia


to talk about this word.