Summation of answers and comments:

Use "an" before a word that begins with a vowel sound,
otherwise, use "a".

Still not clear on which to use before acronyms that can be read as letter-by-letter or as the words they represent.

Side note: In the future, I'll only use acronyms where there is no need for "a" or "an" before them. If an "a" or an "an" is needed, I'll write the words of the acronym.

I'd use: "Nightmare of an operator of N.Y.C.'s subway/Subway..."

Simpler sentence:
Instead of "An NYU student" or "A New York University student",
"A student of NYU" or "A student of New York University".

Original Question:

I'm pretty sure I use the correct "a"/"an".
Something like: if the next word (expanded from acronym, if exists) starts with "a"/"e"/"i"/"o"/"u"(/"y"?) => use "an", otherwise => use "a".

A (bad?) example from "The New Yorker"(!) on YouTube:
"An N.Y.C. Subway Operator's..."

What are the "official" rules?

  • "y" is not a vowel. However some specific words may use an, though I have never encountered one. It will be helpful if someone provides an example of the same. Oct 1 '20 at 11:06
  • In a word like "yclept" (which, however, is an archaism), "y" makes a vowel sound and therefore would be preceded by "an" if there were a valid sentence where it could come directly after an indefinite article. There may be a better example. "Y" also produces a vowel sound in "many" and many other words, but that's irrelevant as it's not the initial sound.
    – rjpond
    Oct 1 '20 at 11:49
  • If you were referring to the Swedish city of Ystad, you'd say "an Ystad resident".
    – rjpond
    Oct 1 '20 at 11:50
  • @rjpond, How is "Ystad" pronounced? "yis-tad" -> "a Ystad", "is-tad" -> "an Ystad" = What sounds right to me and as a comment/answer about vowel-sounding words.
    – iAmOren
    Oct 1 '20 at 13:16
  • Swedish y doesn't exist in the English language but the correct approximation would be eestahd or isstahd, not yistad. But if you did want to pronounce it yistad then it would take "a".
    – rjpond
    Oct 1 '20 at 14:10

You use an when the next word starts with a vowel sound. There is no hard rule as to what letter follows a/an in writing - it's dependent on pronunciation:

an hour ("h" is silent, so the word starts with the sound /a/)

a hit ("h" is not silent in this case, so the word starts with /h/).

an N.Y.C. ("N.Y.C." is pronounced as individual letters, so it starts with /ɛn/ - the first sound is /ɛ/, which is a vowel sound)

  • Thank you. Hmmm... I see, now, why "An N.Y.C" is correct... In my mind I read "An New York City"... How to avoid that - from the perspective of the writer? Simply: "N.Y.C. Subway....."?
    – iAmOren
    Oct 1 '20 at 11:08
  • @iAmOren The use of a*/*an is warranted in this particular headline ("An N.Y.C. Subway Operator's Worst Nightmare") as it doesn't refer to any specific operator (so you can't use the). You could maybe get away with no article since headlines occasionally omit those, but an sounds more natural and proper here. Oct 1 '20 at 11:16
  • 1
    @iAmOren "X's worst nightmare" is an idiom/rhetorical figure and isn't supposed to be understood in a literal way - no reader would read that headline and think "this clip will show what dreams subway operators have". Oct 1 '20 at 11:29
  • 1
    There are occasional differences between British and American English, e.g. "a herb" (most BrE speakers) v "an herb" (most AmE speakers - because they don't pronounce the "h").
    – rjpond
    Oct 1 '20 at 11:52
  • 2
    @iAmOren - "menstruous exaggeration" - does that happen once a bloody month? Oct 1 '20 at 12:14

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