1. adverb
in a way based on reasoning from known facts or past events rather than by making assumptions or predictions."This lays them under a necessity of speaking a posteriori , if I may be allowed the phrase."
2. adjective
relating to or denoting reasoning or knowledge that proceeds from observations or experiences to the deduction of probable causes."This volume presents the most up-to-date information available on a posteriori error estimation for finite element approximation in mechanics and mathematics."