how does this really work?
i always thought "a" was used when the following word began with a consonant and "an" was used when the following word began with a vowel.
however, I was recently told that it wasn't so much what the following word began with, but the rule was based on sound.
so, if the following word begins with a consonant sound you use "a" and if the following word begins with a vowel sound you use "an".
can anyone clarify this for me by showing me a reputable source that explains this rule?