postfacto

Postfacto is a term derived from Latin post factum, meaning after the fact. In English usage, it most often appears as part of the set phrase ex post facto, which in law denotes retroactivity—laws or penalties that apply to events occurring before the law’s enactment. The form postfacto alone is less common in formal legal writing and is typically treated as a nonstandard or informal variant of post facto.

In nonlegal contexts, postfacto can be used more loosely to describe analyses, reflections, or decisions made after an event. For example, postfacto analysis or postfacto review refers to retrospective examination of events, outcomes, or performances, rather than predictions or actions taken beforehand. The term is also encountered in discussions about post-event assessment in fields like business, journalism, and research.

Etymology: from Latin post factum, “after the fact.” The widely used Latin legal construction ex post facto literally means “from after the fact” and is the standard term for retroactive legislation.

See also: ex post facto; post hoc; retrospective analysis; after-action review.

Notes: Because of its variable presence in English, writers often prefer “ex post facto” for legal retroactivity, and “postfacto” may be used only in informal or contextual ways.