definition of a posteriori:
(from Latin. translates to "from what comes after") a process of acquiring knowledge that results from experience or observation, as opposed to knowledge that originates from pure reason.
a posteriori, as it might be used:
The real nature of the action will be discovered from the basic facts a posteriori.
a posteriori, in an example:
Fiona and Fergus, having been married for forty years, know, a posteriori, that compromise is essential to a successful marriage.