I hear the phrase “an American” and wonder why “a American” sounds incorrect. “a [nationalism]” works in every other context. “a Libyan” “a Russian” “a Chinese”. Other examples where “an” sounds correct where “a” does not is “an Apache”. What is the difference between the determiners A and An and why the inconsistency?
It’s a according to the whether the first syllable sound is a vowel sound or constant sound. I specify the syllable sound and not the first letter because it would be “an hour” due to the
h being silent. So if the word starts with a vowel sound use
an, but use
a for words that start with constant sounds.
Source : Link , Question Author : Seph , Answer Author : Diane Rhodes