Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
a-, an- (prefixes)
In some applications, these prefixes derive from the Old English prepositions an and on, meaning “in,” as in asleep, afoot. The Old English prefix a-, meaning “out,” “out of,” or “up,” gives us arise, and from still another Old English prefix, of-, meaning “of” or “off,” we get words like akin. Nautical terms alone made from Old English prefixes are impressively numerous: consider aback, abaft, abeam, adrift, ahead, alee, astern, and awash. The Greek prefix a-/an-, meaning “not,” yields another larger group of words, as in anemic, amoral, atypical, and anesthetic. If the word to which one of these prefixes is to attach itself begins with a consonant, the prefix will be spelled a- as in apolitical; if with a vowel, the prefix will be spelled an- as in anarchy. See AFFIX.
