1. Indefinite Articles: a and an
A and an signal that the noun modified is indefinite, referring to any member of a group. These indefinite articles are used with singular nouns when the noun is general; the corresponding indefinite quantity word some is used for plural general nouns. The rule is:
a + singular noun beginning with a consonant: a boy
an + singular noun beginning with a vowel: an elephant
a + singular noun beginning with a consonant sound: a user (sounds like 'yoo-zer,' i.e. begins with a consonant 'y' sound, so 'a' is used)
some + plural noun: some girls
If the noun is modified by an adjective, the choice between a and an depends on the initial sound of the adjective that immedately follows the article:
a broken egg
an unusual problem
a European country (sounds like 'yer-o-pi-an,' i.e. begins with consonant 'y' sound)
Note also that in English, the indefinite articles are used to indicate membership in a profession, nation, or religion.
I am a teacher.
Brian is an Irishman.
Seiko is a practicing Buddhist.
Found this on NVidia's website...
GeForce 7 Series Products are Available for Purchase NOW!
Purchase an NVIDIA GeForce 7600 GT now through any of the following launch partners: