/ ˌeɪ praɪˈɔːraɪ; NAmE / adjective , adverb
(from Latin , formal ) using facts or principles that are known to be true in order to decide what the probable effects or results of sth will be, for example saying 'They haven't eaten anything all day so they must be hungry.'
—compare a posteriori
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WORD ORIGIN
late 16th cent.: Latin , from what is before .