an
1. an \*n, (')an\ ia [ME, fr. OE a-n one - more at ONE] : A - in standard
speech and writing used (1) invariably before w ords beginning with a vowel
letter and sound {an oak} (2) invariably before h-initial words in which
the h is silent {an honor}; (3) frequently before h-initial words which
have in an initial unstressed syllable an /h/ sound often lost after the an
{an historian} (4) sometimes esp. in England before words like union and
European whose initial letter is a vowel and whose initial sounds are /yu:/
or /yu./
2. an or an' \see AND\ \(')an\ cj substand 1: AND archaic 2: IF