Why you should know: The ‘a’ vs ‘an’ conundrum is not about what letter actually begins the word, but instead about how the sound of the word starts.
For example, the ‘h’ in ‘hour’ is silent, so you would say ‘an hour’ and not ‘a hour’. A trickier example is Ukraine: because the ‘U’ is pronounced as ‘You’, and in this case the ‘y’ is a consonant, you would say “a Ukraine” and not “an Ukraine”.
Tip: when in doubt, sound it out(loud).
Thank you for coming to my TED talk.
I’ve seen a good 15 minute essay-video about this:
https://youtu.be/nCe7Fj8-ZnQ
TLDW: English speakers increasingly use the consonant versions of “a(n)”, “the” and “to” for anything in casual conversation, just with a glottal stop to separate vowel sounds. This is then found more and more in written and formal language.