(ən; ăn when stressed)
indef.art. The form of
a used before words beginning with a vowel or with an unpronounced
h: an elephant; an hour. See Usage Notes at
a2,
every.
The forms of the indefinite article are good examples of what can happen to a word when it becomes habitually pronounced without stress.
An is in fact a weakened form of
one; both
an and one come from Old English
ān “one.” In early Middle English, besides representing the cardinal numeral “one,”
ān developed the special function of indefinite article, and in this role the word was ordinarily pronounced with very little or no stress. Sound changes that affected unstressed syllables elsewhere in the language affected it also. First, the vowel was shortened and eventually reduced to a schwa (ə). Second, the
n was lost before consonants. This loss of
n affected some other words as well; it explains why English has both
my and
mine, thy and
thine. Originally these were doublets just like
a and
an, with
mine and
thine occurring only before vowels, as in Ben Jonson's famous line “Drink to me only with thine eyes.” By the time of Modern English, though,
my and
thy had replaced
mine and
thine when used before nouns (that is, when not used predicatively, as in
This book is mine), just as some varieties of Modern English use
a even before vowels
(a apple).