a posteriori Look up a posteriori at Dictionary.com
17c., in reference to reasoning from a consequent to its antecedent, from an effect to its cause; Latin, literally "from what comes after;" from a "off, away from," usual form of ab before consonants (see ab-) + posteriori, neuter ablative of posterius, comparative of posterus "after, subsequent," from post "after" (see post-). Opposed to a priori. In modern use (from c. 1830, based on Kant) roughly equivalent to "from experience."