In elementary school, most of us learned that it is proper to
use “an” before a word that begins in a vowel. Otherwise, use
“a”. However, the English language has exceptions to every rule.
This is no different. For example, “an hour” is proper as
opposed to “a hour”. So why do we come across “an historic” when
historic begins with “h”? Don’t we all pronounce the “h” in
historic? Sort of. “H” is a weak consonant and pronounced
differently across the world, which affects our choice of
indefinite article (a or an). Is there an answer? Yes. Historic
is correctly pronounced with the “h” and therefore requires “a”
before it. So, the correct pairing of words is “a historic.”