YSK: Use ‘a’ when the word starts with a consonant sound, and ‘an’ when it starts with a vowel sound
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”.
Kids are frequently taught that letters are vowels (or consonants) when it’s actually the sounds they represent, and there’s not a 1:1 mapping between letters and sounds.