Actually, you do NOT decide whether to use an "a" or an "an" before word based on the FIRST LETTER of that word. INSTEAD, you decide based on the FIRST SOUND of the word. If the first sound of the word is a vowel sound, then use "an" in front of it.
For example, we say "a unicorn" because the first sound in "unicorn" is "y" even though the word starts with a vowel ("u").
Dr. Kathryn H.
No. That’s wrong. It has nothing to do with the vowel as beginning letter; it is the beginning vowel SOUND. You don’t say “an United Nation” and expect to be taken seriously as a speaker. “United” begins with a “y” sound despite beginning with a vowel letter. Same with “an historic event.” Some people claim this one depends on the regional dialect, but I contend again that you would not say “a historic event,” with all the emphasis on the hiss, and expect to be taken seriously as a speaker.04/10/21