Ab- pref.

repr. L. ab, prep. ‘off, away, from,’ cogn. w. Gr. ἀπό, Skr. apa, OTeut. af, OE. of, mod. E. of, off, mod. G. ab. In L. it was reduced to a- before p-, m-, and v-, became au- before f-, and abs- before c- and t-. The form ab- was in OFr. generally retained as in abusum, abus; sometimes changed to av- as in abortionem, avortion; sometimes reduced to a- as in abbreviāre, abregier, abridge. Ab- appears in Eng. in words that have lived on through OFr. as abuse; that have been adapted or formed in later Fr. as absorb; or have been adapted or formed in Eng. as ablaqueate, abhominal, abarticulation. Quite recent, and apparently suggested by ab-normal, are formations like ab-oral, ab-actinal, in which ab- is used for ‘position away from.’