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ab- Prefix indicating "off" or "away"

Not a productive prefix in Spanish, it occurs as a relic in verbs like abrir. From Latin ab 'id.' From Proto-Italic *ap- 'id.' From Proto-Indo-European *h2epo 'id.' As an allative preposition, the word had a full grade in ab- and a zero grade *h2po, preserved in po-.

Italic: Umbrian ap-, Paelignian af-, Oscan af-

Indo-European: Germanic: Gothic af, aff-, Old Norse af, Old High German aba, Old Saxon af, English of; Balto-Slavic: Lithuanian po-, Latvian ap "beneath," Old Church Slavonic po, Russian po; Albanian: pa "without;" Hellenic: Ancient Greek ἀπό (apó) "far from;" Indo-Iranian: Sanskrit ápa "away," Avestan apa-; Anatolian: Hittite appā "behind"