Determining whether to use “a” versus “an” should not be confusing, but it is.
This week, I had a prolonged discussion with a co-worker about why “an MRI” is correct and “a MRI” is not.
It turns out that many of us were taught the wrong rules for use of the indefinite articles. I remember being told to use “an” when the word preceding it starts with a vowel and to use “a” when the word preceding it starts with a consonant.
The rules actually say to use “an” before any word beginning with a vowel sound and to use “a” before any word beginning with a consonant sound. No matter how the word is spelled, “a” comes before words with a consonant sound, including /y/,/h/, and /w/. Likewise, no matter how it’s spelled, “an” comes before a word with a vowel sound.
Take these examples:
Here are a couple of example sentences: