alpha privative

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The prefix a- or an- before vowels, used in Greek and in English words borrowed from Greek to express absence or negation.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun grammar The prefix a- (or an- when prefixing a root which begins with a vowel) found in some English words of Greek derivation. It expresses negation or absence. The prefix has cognates in other Indo-European languages, including in- in Latin and un- in English.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the negative prefix a- or un-