Alpha privative

An alpha privative or, rarely,[1] privative a (from Latin alpha prīvātīvum, from Ancient Greek α στερητικόν) is the prefix a- or an- (before vowels) that is used in Indo-European languages such as Sanskrit and Greek and in words borrowed therefrom to express negation or absence, for example the English words atypical, anesthetic, and analgesic.

It is derived from a Proto-Indo-European syllabic nasal *n̥-, the zero ablaut grade of the negation *ne, i.e. /n/ used as a vowel. For this reason, it usually appears as an- before vowels (e.g. an-alphabetism, an-esthesia, an-archy).[2] It shares the same root with the Greek prefix nē- or ne-, in Greek νη- or νε-, that is also privative (e.g. ne-penthe).[3]

It is not to be confused with, among other things, an alpha copulative (e.g. a-delphi) or the prepositional component an- (i.e. the preposition ana with ecthlipsis or elision of its final vowel before a following vowel; e.g. an-ode).