h₂epo
“off, away, behind”behind/away
PIE preposition meaning off, away, or behind. Source of English "after," Latin ab, and Greek apo.
Discussion
*h₂epo is a Proto-Indo-European preposition meaning "off," "away," or "behind," closely related to *h₂ep- and *h₂epi in the PIE spatial system.
The root gives Old English æfter "after" (modern English after, from a comparative form meaning "more off/behind") and of "from, off" (modern English of). German nach "after" may be related through a different derivation. The Germanic sense of "behind in time" develops naturally from the spatial "behind."
Latin ab "from" and Greek apó "away from" are sometimes derived from this form rather than *h₂ep-, though the precise distribution between these closely related roots is debated. Sanskrit ápa "away" likely reflects this root.
The distinction between *h₂ep-, *h₂epi, and *h₂epo may represent different case forms or derivations of a single spatial root, with specialization in different daughter languages. The three forms create a micro-system: *h₂ep- (separation), *h₂epi (proximity/surface), *h₂epo (posterior position).
Modern descendants include English after, aft, of, off, and potentially the ab- and apo- prefixes, though these are more commonly assigned to *h₂ep-.
Notes
Source of Latin "ab/abs", Sanskrit "ápa". Posterior/ablative spatial marker.